GB2517967A

GB2517967A - Twist-lock collar

Info

Publication number: GB2517967A
Application number: GB1315924.9A
Authority: GB
Inventors: Russell Allen
Original assignee: STRAINSTALL UK Ltd
Current assignee: STRAINSTALL UK Ltd
Priority date: 2013-09-06
Filing date: 2013-09-06
Publication date: 2015-03-11
Anticipated expiration: 2033-09-06
Also published as: GB201315924D0; GB2517967B; WO2015033158A1

Abstract

A twist lock collar 126 comprises an aperture (140, fig 3) and a projection 150. The projection 150 comprises a rotation feature 152 offset from a longitudinal axis of the twist lock shaft 124 and is engagable with a rotation assembly. A load held by the twist lock 120 is transferred through the twist lock collar 126 to a container spreader (10, fig 1). The twist lock collar 126 forms a load cell, which may comprise one or more strain gauges (160, fig 6), a housing portion 136 and a cover portion 138. The twist lock collar 126 may also be at least partly hollow, the hollow 132 may include an annular channel 137 in the housing portion 136. The strain gauges (160, fig 6) may be located on an upper surface 134 inside the hollow 132. The housing 136 and cover 138 portions may define the hollow 132 between them and a hub 142 which defines the aperture 140 for receiving the twist lock shaft 124. The collar 126 may comprise a cable connection point 148 which may be on a top or side surface of the collar 126 and opposite the rotation feature 152. The collar 126 may comprise one or more passages (156, fig 3) for distributing a lubricant. There may also be a base plate 170 between the collar 126 and the surface of the container spreader (10, fig 1). The base plate 170 may overlap an annular recess in the surface of the container spreader (10, fig 1).

Description

TWIST-LOCK COLLAR

The present disclosure relates to a twist-lock collar and particularly but not exclusively relates to a shipping container twist-lock collar for a container spreader twist-lock.

Background

A container spreader is a device used for engaging and lifting containers, such as shipping containers. A side view of such a container spreader 10 is shown in Figure 1.

The container spreader 10 can be used in conjunction with a container crane, a straddle carrier or with any other container lifting machinery to selectively engage and lift containers (not shown) The container spreader 10 comprises four corners (two of which are shown in Figure 1) and at each corner there is a locking device, which is typically known as a twist-lock 20.

The twist-lock 20 comprises a bulbous end 22 provided at an end of a twist-lock shaft 24. The bulbous end 22 is configured to selectively enter an opening in a corner of the container. The bulbous end 22 and opening of the container are elongate in a direction perpendicular to a longitudinal axis of the twist-lock shaft 24. Accordingly, the bulbous end 22 may enter the opening in a first rotational position of the twist-lock and the bulbous end 22 may not be withdrawn from the opening in a second rotational position.

The twist-locks may thus be rotated to selectively engage the container.

Rotation of the twist-lock 20 is facilitated by a linkage 30, which is coupled to a twist-lock collar 26. The twist-lock collar 26 is disposed about and rotatably coupled to the twist-lock shaft 24. The twist-lock collar 26 comprises a radial projection 28 which is pivotably connected to the linkage 30. The linkage 30 may be connected to one or more of the twist-locks 20 and movement of the linkage 30 causes the twist-locks to rotate between the first and second rotational positions.

It will be appreciated that it is desirable to weigh the container being lifted by the container spreader, for example to check that the container does not exceed certain weight limits By way of example, EP2019808B1 discloses a twist-lock comprising an optical fiber stress sensor inserted into a longitudinal channel in the twist-lock shaft.

However, such systems require bespoke twist-locks, add to the complexity of the twist-lock and are difficult to repair or replace in the field.

The present disclosure seeks to address these issues.

Statements of Invention

According to a first aspect of the present disclosure there is provided a container spreader twist-lock collar for a twist-lock of a container spreader, the twist-lock collar comprising: an aperture for receiving a shaft of the twist-lock, wherein the twist-lock collar is rotatably coupleablo, e.g. lockable, to the shaft of the twist-lock, a projection comprising a rotation feature offset from a longitudinal axis of the twist-lock shaft, the rotation feature being configured for engagement with a rotation assembly so that the twist-lock may be selectively rotated by the rotation assembly about the longitudinal axis of the twist-lock shaft; wherein the twist-lock collar is configured to be in a load path from the container spreader to a container being carried by the container spreader, such that a load held by the twist-lock is transferred to the container spreader via the twist-lock collar, and wherein the twist-lock collar forms a load cell configured to measure the load being carried by the twist-lock.

The twist-lock collar may be configured to withstand the torsional and axial forces applied to it and at the same time permit sufficient flex so that the axial load applied to the twist-lock collar can be measured.

The twist-lock collar may comprise one or more strain gauges configured to measure the load being carried by the twist-lock.

The twist-lock collar may be at least partially hollow. The hollow may be annular. The hollow may extend circumferentially about the shaft longitudinal axis.

The strain gauges may be located on a surface inside the hollow collar. The strain gauges may be located on an upper and/or lower surface inside the hollow collar, e.g. when the twist-lock collar is in an installed configuration.

The twist-lock collar may further comprise a housing portion and a cover portion. The housing portion and cover portion may be configured so as to define a hollow between the housing portion and cover portion. The housing portion may define an annular channel. The annular channel may have a U-shaped cross-section. The cover portion may be annular and may cover the annular channel. In an installed configuration, the cover portion may be provided above or below the housing portion. The cover portion and housing portion may be joined, e.g. welded, together to form a hermetically sealed hollow chamber.

The housing portion and/or the cover portion may define a hub. The hub may define the aperture for receiving the shaft of the twist-lock.

The twist-lock collar may further comprise a cable connection point. The cable connection point may be configured to receive an electrical cable for transferring data and/or power. The cable connection point may be arranged so that when the cable is installed, the cable may at least initially extend in a direction that may be substantially parallel to the longitudinal axis of the twist-lock shaft. The cable connection point may be on a top surface of the twist-lock collar. The cable connection point may be on a side surface of the twist-lock collar. In either case, the cable connection point may be diametrically opposite the projection comprising the rotation feature.

The twist-lock collar may comprise one or more passages for distributing a lubricant, such as oil, to one or more surfaces of the twist-lock collar. The passages may extend through a hub wall. At least one of the passages may extend substantially longitudinally through the hub wall, e.g. to transmit the lubricant between upper and lower surfaces of the twist-lock collar. One or more further passages may extend radially through the hub wall, e.g. to transmit lubricant to a surface of the hub facing the twist-lock shaft. The one or more further passages may be in fluidic communication with the longitudinally extending passages. A substantially circumferential groove may be provided on one or both of the axial end surfaces of the hub, e.g. to transmit lubricant about the circumference of the hub. The circumferential grooves may be in fluidic communication with the longitudinally extending passages.

The twist-lock collar may comprise an engagement feature for rotatably coupling the twist-lock collar to the shaft of the twist-lock. The engagement feature may comprise a protrusion (e.g. a key), a recess (e.g. a keyway), or any other feature suitable for rotatably linking the twist-lock collar to the twist-lock shaft.

The projection may extend in a direction substantially parallel or perpendicular to the longitudinal axis, e.g. the projection may extend radially or longitudinally. The rotation feature may comprise a recess, a protrusion or a surface. For example, the projection may extend radially and the rotation feature may form a pivot point, which may engage with the rotation assembly, which may be in the form of a linkage. However, a motor or any other actuator may engage with the projection to cause the twist-lock collar, and thus the twist-lock to rotate.

The twist-lock collar may rotate with respect to a surface of the container spreader.

The twist-lock collar may directly or indirectly engage the surface of the container spreader.

A twist-lock collar assembly may comprise the above-mentioned twist-lock collar. The twist lock collar assembly may further comprise a base plate. The base plate may be configured for placement between the twist-lock collar and a surface of the container spreader. The base plate may rest on the surface of the container spreader when in an installed configuration. The twist-lock collar may in turn rest on the base plate when in the installed configuration.

The base plate may be sized so as to overlap, e.g. overhang, one or more annular recesses in the surface of the container spreader. In other words, the base plate may be sized so as to be greater than the diameter of one or more annular recesses in the surface of the container spreader. The annular recesses may be disposed about an opening on the surface of the container spreader that receives the twist-lock. As such, the base plate may be configured so that an annular recess is formed between the base plate and the surface of the container spreader when in the installed configuration.

A container spreader twist-lock may comprise the above-mentioned twist-lock collar or the above-mentioned twist-lock collar assembly.

According to a second aspect of the present disclosure there is provided a method of installing a container spreader twist-lock collar, the method comprising providing the above-mentioned twist-lock collar or the above-mentioned twist-lock collar assembly and installing the twist-lock collar or twist-lock collar assembly to a twist-lock for a container spreader. For example, the twist-lock collar or twist-lock collar assembly may be retrofitted to an existing twist-lock.

The twist-lack collar of the present disclosure may be configured to advantageously withstand the torsional and axial forces applied to it and at the same time permit sufficient flex so that the axial load applied to the twist-lock collar can be measured, e.g. reliably and accurately.

As mentioned above, the twist-lock collar of the present disclosure may be readily retrofitted to an existing twist-lock without having to reconfigure the twist-lock or alter its position or performance. The twist-lock collar of the present disclosure may be sized to replace an existing twist-lock collar and other separate load cells may not be required.

Accordingly, the twist-lock collar of the present disclosure advantageously minimises the number of components. In addition, with the twist-lock collar of the present disclosure, a load cell may thus be readily applied to a twist-lock without for example having to bore out the shaft of the twist-lock.

The twist-lock collar of the present disclosure also ensures that a maximum length of the twist-lock shaft is exposed below the container spreader since a separate load cell disposed about the twist-lock shaft is not required. Maximising the exposed length of the twist-lock shaft may facilitate engagement with the container, for example when the container is resting at an angle.

Brief Description of the Drawings

For a better understanding of the present disclosure, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a side view of a previously-proposed twist-lock assembly and container spreader; Figure 2 is a perspective view of a twist-lock comprising a twist-lock collar according to

an example of the present disclosure;

Figure 3 is a perspective view of the twist-lock collar according to the example of the

present disclosure;

Figures 4a and 4b are top and side views respectively of the twist-lock collar according

to the example of the present disclosure;

Figures 5a and 5b show the twist-lock comprising the twist-lock collar according to an example of the present disclosure in an installed configuration with Figure 5a showing a side view and Figure Sb showing a sectional view corresponding to section X-X marked on Figure 5a; Figure 6 is a view of a housing portion of a twist-lock collar according to a further

example of the present disclosure;

Figure 7 is a sectional view of an annular hollow in the housing portion according to the

example of the present disclosure; and

Figures Ba and 8b show in schematic form an arrangement of strain gauges according

to the example of the present disclosure.

Detailed Description

With reference to Figures 2 to 5 a twist-lock collar 126 for a container spreader twist-lock 120 according to an example of the present disclosure is shown. The twist-lock collar 126 comprises an aperture 140 which receives a shaft 124 of the twist-lock when installed. The twist-lock collar 126 further comprises a projection 150 comprising a rotation feature 152 offset from a longitudinal axis of the twist-lock shaft 124. The rotation feature 152 is configured for engagement with a rotation assembly, e.g. in the form of linkage 30 (see Figure 1), so that the twist-lock may be selectively rotated by the rotation assembly about the longitudinal axis of the twist-lock shaft.

As depicted, the projection 150 extends in a direction substantially perpendicular to the longitudinal axis, e.g. the projection extends in a substantially radial direction.

However, it is also envisaged that the projection may extend in a direction substantially parallel to the longitudinal axis or any other direction between these perpendicular and parallel directions. Furthermore, as depicted the rotation feature 152 comprises a recess 154. The recess 154 may receive a pin 34 (see Figure 1), which may rotatably connect the projection 150 to the linkage 30 such that the linkage may rotate with respect to the projection. The rotation feature 152 may however comprise a protrusion for engaging the linkage 30 or any other feature for engaging the rotation assembly.

The twist-lock collar 126 is rotatably coupleable, e.g. linkable, to the shaft 124 of the twist-lock such that the twist-lock collar 126 is constrained to rotate with the shaft 124.

Accordingly, the twist-lock collar 126 may comprise an engagement feature for rotatably coupling the twist-lock collar 126 to the shaft 124 of the twist-lock. For example, the twist-lock collar 126 may comprise a recess 128 (e.g. a keyway), which, as shown En Figure Sb, engages a key 130, which in turn engages a recess in the shaft 124. The twist-lock collar recess 128 may be longitudinally disposed and may extend over the length of the twist-lock collar. It will be appreciated that in alternative arrangements, the twist-lock collar engagement feature may comprise a protrusion (e.g. a key), which may or may not be integral to the twist-lock collar.

In an installed configuration, the twist-lock collar 126 may directly or indirectly rest on an upper facing surface 32 of the container spreader 10, which is shown in Figures 1 and Sb. In addition, the twist-lock collar 126 may rotate with respect to the surface 32 of the container spreader 10. As depicted in Figures 2 and 5, a base plate 170 may be provided between the twist-lock collar 126 and surface 32 of the container spreader 10.

The base plate 170 may be a separate component or the base plate may be integral with the twist-lock collar 126. The twist-lock collar 126 may rotate relative to the base plate 170 and/or the base plate 170 may rotate relative to the surface 32. A nut 180 provided on an end of the shaft 124 and above the twist-lock collar 126 may hold the assembly in place.

The surface 32 of the container spreader 10 comprises an opening 36 to receive the twist-lock shaft 124. One or more annular recesses 33 may be provided about the opening 36 on the surface 32. As shown in Figure 5b, the base plate 170 may be sized so as to extend over the one or more annular recesses 33 in the surface 32 of the container spreader 10. In other words, the radial dimensions of the base plate 170 may be sized so as to be greater than the diameter of the one or more annular recesses 33 in the surface of the container spreader. The twist-lock collar 126 may have substantially the same radial dimensions, e.g. diameter, as the base plate 170.

As is also shown in Figure Sb, the base plate 170 may comprise a hub 172 which may extend into the opening 36 on the surface 32 of the container spreader that receives the twist-lock. The hub 172 may comprise a keyway 174, which may allow the base plate 170 to pass over the key 130. However, as depicted, the hub keyway 174 may not engage the key 130 in an installed configuration. The twist-lock collar 126 may therefore be able to rotate relative to the base plate 170.

The twist-lock collar 126 is configured to be in a load path from the container spreader 10, via surface 32, to a container being carried by the container spreader, such that a load held by a bulbous end 122 of the twist-lock is transferred to the container spreader via the twist-lock collar. According to the present disclosure, the twist-lock collar 126 forms a load cell configured to measure the load being carried by the twist-lock. The twist-lock collar may comprise one or more strain gauges 160 (shown in Figures 6 and 7), which are configured to measure the load being carried by the twist-lock. The recess 33 in the surface 32 of the container spreader 10 may permit the base plate 170 and thus the twist-lock collar 126 to flex. The strain gauges 160 may be configured to measure such a flex in the twist-lock collar 126.

With reference to Figure Sb, the twist-lock collar 126 may be at least partially hollow, e.g. such that the twist-lock collar comprises a hollow 132. The hollow 132 may be annular, e.g. with the hollow extending circumferentially about the shaft longitudinal axis. The hollow 132 may facilitate the flex of the twist-lock collar 126.

Referring still to Figure 5b, the twist-lock collar 126 may further comprise a housing portion 136 and a cover portion 138. The housing portion 136 and cover portion 138 may be configured so as to define the hollow 132 between the housing portion and cover portion. As depicted, the housing portion 136 may define an annular channel 137 and, as shown in Figure 7, the annular channel 137 may have a substantially U-shaped cross-section. The cover portion 138 may comprise a substantially flat annular plate and may cover the annular channel 137. In an installed configuration, the cover portion 138 may be provided below the housing portion 136, although in an alternative arrangement the cover portion 138 may be provided above the housing portion 136.

The cover portion 138 and housing portion 136 may be joined, e.g. welded, together to form a hermetically sealed hollow chamber.

The housing portion 136 and/or the cover portion 138 may define a hub 142. A radially inner side wall 144 of the housing portion may define the hub. The hub 142 may extend beyond a top surface 139 of the housing portion 136. The hub 142 may in turn define the aperture 140 for receiving the shaft 124 of the twist-lock. Furthermore, the projection 150 may extend from the housing portion 136, e.g. from a radially outer side wall 146 of the housing portion 136. The radially inner and outer side walls 144, 146 may also form sidewalls of the annular channel 137. An annular, e.g. plate-shaped, wall 145 may join the inner and outer side walls 144, 146 so as to complete the channel 137. The twist-lock collar 126 may be substantially cylindrical in shape.

However, a portion of an outer side surface 141 of the twist-lock collar may be flat and the projection 150 may extend from this flat portion.

The thickness of one or more of the walls 144, 145, 146 of the twist-lock collar 126 may be sized so that the twist-lock collar can withstand the torsional forces applied to the twist-lock collar by the rotation assembly via the projection 150. Furthermore, the thickness of one or more of the walls 144, 145, 146 of the twist-lock collar 126 may be sized so that the twist-lock collar can withstand the axial forces applied to it by the load of a container On the other hand, the thickness of one or more of the walls 144, 145, 146 of the twist-lock collar 126 may also be sized to permit sufficient flex so that the axial load applied to the twist-lock collar may be reliably and accurately measured, By way of example, the thickness of inner side wail 144 may be between 15% and 25% of an inner hub diameter of the twist-lock collar; the thickness of outer side wall 146 may be between 5% and 35% of the inner hub diameter of the twist-lock collar; and/or the thickness of the annular wall 145 may be between 10% and 20% of the inner hub diameter of the twist-lock collar. in a particular example, the thickness of inner side wall 144 may be approximately 21% of the inner hub diameter of the twist-lock collar; the thickness of outer side wall 146 may be approximately 27% of the inner hub diameter of the twist-lock collar; and/or the thickness of the annular wall 145 may be approximately 15% of the inner hub diameter of the twist-lock collar. The inner side wall 144 thickness may be locally reduced at the keyway recess 128. The outer side wall 146 thickness may also be locally reduced at the flat portion of outer side surface 141, e.g. such that the thickness of outer side wall 146 may be approximately 11% of the inner hub diameter of the twist-lock collar.

The strain gauges 160 may be located on a surface inside the hollow 132 of the twist-lock collar 126. In particular, as shown in Figure 7, the strain gauges may be located on an upper surface 134 inside the hollow 132, e.g. when the twist-lock collar is in an installed configuration. In alternative arrangements, the strain gauges may be located on a lower surface, side surface or combination of surfaces inside the hollow 132, Furthermore, as depicted in Figure 7, the strain gauges 160 may be disposed at the edge of a surface. A portion of the strain gauge may be adjacent to or overlap a corner 133a, 133b of the hollow 132, e.g. where the side walls 144, 146 meet the upper surface 134. The corners 133a, 133b may be radiused and the portion of the strain gauge may be provided on the radius of the corner. As depicted in Figure 6, the strain gauges 160 may be orientated such that connection points 161 for each strain gauge may be provided away from the corners 133a, 133b. In addition to the strain gauges 160, any supporting electronics, e.g. signal amplifiers, may be provided in the hollow 132.

Referring to Figure 6, the strain gauges 160 may be circumferentially distributed, e.g. equiangularly, about the twist-lock collar hollow 132. For example, there may be eight strain gauges arranged at 45° intervals about the longitudinal axis. However, the radial position of the strain gauges 160 may vary. For example, alternating strain gauges may be disposed at alternate first and second radial positions. The first radial position may correspond to a radially outermost corner of the surface 134 and the second radial position may correspond to a radially innermost corner of the upper surface 134. In this manner, half of the strain gauges 160a, 160c, 160e, 160g may be equiangularly arranged, e,g. at 90° intervals, and may be provided at the radially innermost position.

The remaining half of the strain gauges 160b, 160d, 160f, 160h may be interspersed between the strain gauges I 60a, 1 60c, 1 60e, 1 60g and may be provided at the radially outermost position. The radially innermost strain gauges 160a, 160c, 160e, 160g may detect tensile loads whilst the radially outermost strain gauges 160b, 160d, 160f, 160h may detect compressive Foads by virtue of the flexing of the twist-lock collar 126 when a load is applied to the twist-lock.

Figure 8 shows a wiring arrangement for the strain gauges 160. The strain gauges 160 may be arranged to form a Wheatstone bridge, for example with strain gauges arranged between each of the four connection points 1 62a, 1 62b, 1 62c, 1 62d of the Wheatstone bridge. In the particular example shown, a pair of strain gauges may be provided between each connection point 162. Pairs of the radially outermost strain gauges 160b, 160d, 1601, 160h may be disposed opposite one another in the Whetstone bridge. Similarly, pairs of the radially innermost strain gauges 160a, 160c, 160e, 160g may be disposed opposite one another in the Whetstone bridge and between the pairs of the radially outermost strain gauges. In this way, the load on the twist-lock collar may be inferred from the changes in resistance between the connection points 162a, 162b, 162c, 162d of the Wheatstone bridge.

Returning to Figures 2 to 4, the twist-lock collar 126 may further comprise a cable connection point 148. The cable connection point 148 may be configured to receive an electrical cable 149 for transferring data and/or power to or from the twist-lock collar 125. The cable connection may extend into the hollow 132, e.g. to connect the cable to the strain gauges 160 and/or associated electronics. As shown in Figure 2, the cable connection point 148 may be arranged so that when the cable 149 is installed, the cable may at least initially extend in a direction that may be substantially parallel to the longitudinal axis of the twist-lock shaft 124. As is depicted in Figures 2 and 3, the cable connection point 148 may be provided on the top surface 139 of the housing portion 136. However, in an alternative arrangement, which is depicted in Figure 6, the cable connection point 148 may be provided on the outer side wall 146 of the twist-lock collar. In either case, the cable connection point 148 may be provided at a point diametrically opposite the projection 150 comprising the rotation feature. In this way, the cable may be kept out of the way of the rotation mechanism, e.g. linkage 30, so as to reduce the likelihood of the cable interfering with the rotation mechanism.

With reference to Figures 3 and 4a, the twist-lock collar 126 may comprise one or more passages 156 arranged for distributing a lubricant, such as oil, to one or more surfaces of the twist-lock collar. The passages 156 may extend through the hub 142, e.g. the inner side wall 144. For example, one or more first passages 156a may extend substantially longitudinally through the hub wall 142 to transmit the lubricant between upper and lower surfaces of the twist-lock collar. One or more second passages 1 56b may extend radially through the hub wall to transmit lubricant to a surface 143 of the hub 142 facing the twist-lock shaft 124. The second passages 15Gb may be in fluidic communication with the first passages 156a. In addition to the passages 156, a substantially circumferential groove 158 may be provided on one or both of the axial end surfaces 159 of the hub, e.g. to transmit lubricant about the circumference of the hub. The circumferential grooves 158 may be in fluidic communication with the first passages 1 56a. The lubricant may facilitate rotation of the twist-lock collar 126 relative to the base plate 170, surface 32 or nut 180. A lubricant inlet 155, such as a grease nipple, may be provided on the twist-lock collar 126, e.g. on the side wall 146, to provide lubricant to the passages 156. The lubricant inlet 155 may be in fluidic communication with the passages 156 via a further passage (not shown).

In addition to the above-described apparatus, the present disclosure also relates to a method of installing a container spreader twist-lock collar. The method comprises installing the twist-lock collar 126 to a twist-lock 120 for a container spreader 10. With the nut 180 removed, the twist-lock shaft may be inserted through the opening 36 on the surface 32 of the container spreader. The twist-lock collar 126 and the optional base plate 170 may be passed over the top end of the twist-lock shaft 124. The nut 180 may then secure the assembly in place. The twist-lock collar 126 may be retrofitted to an existing twist-lock.

Claims

Claims 1 A container spreader twist-lock collar for a twist-lock of a container spreader, the twist-lock collar comprising: an aperture for receiving a shaft of the twist-lock, wherein the twist-lock collar is rotatably coupleable to the shaft of the twist-lock; and a projection comprising a rotation feature offset from a longitudinal axis of the twist-lock shaft, the rotation feature being configured for engagement with a rotation assembly so that the twist-lock may be selectively rotated by the rotation assembly about the longitudinal axis of the twist-lock shaft; wherein the twist-lock collar is configured to be in a load path from the container spreader to a container being carried by the container spreader, such that a load held by the twist-lock is transferred to the container spreader via the twist-lock collar, and wherein the twist-lock collar forms a load cell configured to measure the load being carried by the twist-lock.
2. The twist-lock collar as claimed in claim 1, wherein the twist-lock collar comprises one or more strain gauges configured to measure the load being carried by the twist-lock.
3, The twist-lock collar as claimed in claim 1 or 2, wherein the twist-lock collar is at least partially hollow.
4. The twist-lock collar as claimed in claims 1 and 2, wherein the strain gauges are located on a surface inside the hollow collar.
5. The twist-lock collar as claimed in claim 4, wherein the strain gauges are located on an upper surface inside the hollow collar.
6. The twist-lock collar as claimed in any of claims 3 to 5, wherein the hollow is annular and extends circumferentially about the longitudinal axis of the twist-lock shaft.
7. The twist-lock collar as claimed in any preceding claim, wherein the twist-lock collar further comprises a housing portion and a cover portion.
8. The twist-lock collar as claimed in claim 7, wherein the housing portion and cover portion are configured so as to define a hollow between the housing portion and cover portion.
9. The twist-lock collar as claimed in claim 7 or 8, wherein the housing portion and/or the cover portion define a hub which defines the aperture for receiving the twist-lock shaft.
10. The twist-lock collar as claimed in any preceding claim, wherein the twist-lock collar further comprises a cable connection point, the cable connection point being configured to receive an electrical cable for transferring data and/or power.
11. The twist-lock collar as claimed in claim 10, wherein the cable connection point is arranged so that when the cable is installed the cable at least initially extends in a direction substantially parallel to the longitudinal axis of the twist-lock shaft.
12. The twist-lock collar as claimed in claim 10 or lit wherein the cable connection point is on a top surface of the twist-lock collar.
13. The twist-lock collar as claimed in claim 10 or 11, wherein the cable connection point is on a side surface of the twist-lock collar.
14. The twist-lock collar as claimed in any of claims 10 to 13, wherein the cable connection point is diametrically opposite the projection comprising the rotation feature.
15. The twist-lock collar as claimed in any preceding claim, wherein the twist-lock collar comprises one or more passages for distributing a lubricant to one or more surfaces of the twist-lock collar.
16. A twist-lock collar assembly comprising the twist-lock collar of any of claims ito and a base plate, the base plate being configured for placement between the twist-lock collar and a surface of the container spreader.
17. The twist-lock collar assembly of claim 16, wherein the base plate is sized so as to overlap an annular recess in the surface of the container spreader.
18. A container spreader twist-lock comprising the twist-lock collar of any of claims 1 to 15 or the twist-lock collar assembly of claims 16 or 17.
19. A method of installing a container spreader twist-lock collar, the method comprising providing the twist-lock collar of any of claims ito 15 or the twist-lock collar assembly of claims 16 or 17 and installing the twist-lack collar or twist-lock collar assembly to a twist-lock for a container spreader.
20. A container spreader twist-lock collar, twist-lock collar assembly or twist-lock substantially as described herein with reference to and as shown in Figures 2 to 8.
21. A method of installing a container spreader twist-lock collar or a twist-lock collar assembly substantially as described herein.