Abstract
A spreader for lifting a transport container comprises a main frame (26) suspended in a main frame suspension arrangement (36) to enable translation along a longitudinal axis (L). The main frame (26) is vertically supported by the main frame suspension arrangement (36) along a support line extending between a first support end (68a) and a second support end (68b), and the main frame suspension arrangement (36) carries the weight of a suspension arrangement load comprising the main frame (26), container connector arrangements (28a, 28b), and any container(s) attached to the container connector arrangements (28a, 28b). A detector arrangement is configured to detect if a centre of mass of the suspension arrangement load is positioned at a longitudinal position along the support line which is beyond a limit position.
Claims
1-26. (canceled)
27. A spreader for lifting a transport container, the spreader comprising a main frame having a first end and a second end, and extending along a longitudinal axis between said first end and said second end, the first end carrying a first container connector arrangement and the second end carrying a second container connector arrangement, each of said first and second container connector arrangements being configured to engage with a transport container; and a main frame suspension arrangement, wherein the main frame is translatably suspended in said main frame suspension arrangement to enable translation along said longitudinal axis, wherein the main frame is configured to be vertically supported by the main frame suspension arrangement along a support line extending between a first support end and a second support end, the main frame suspension arrangement carrying the weight of a suspension arrangement load comprising the main frame, the container connector arrangements, and any container attached to the container connector arrangements; and a detector arrangement configured to detect if a centre of mass of the suspension arrangement load is positioned at a longitudinal position along the support line which is beyond a limit position.
28. The spreader according to claim 27, wherein a support end is said limit position.
29. The spreader according to claim 28, wherein the detector arrangement is configured to detect if said centre of mass is positioned at a longitudinal position beyond any of said support ends.
30. The spreader according to claim 29, wherein the detector arrangement is configured to determine whether said centre of mass is positioned beyond said first support end or beyond said second support end.
31. The spreader according to claim 27, wherein the detector arrangement is configured to detect a change in an angle formed between the main frame and the main frame suspension arrangement.
32. The spreader according to claim 27, wherein the detector arrangement is configured to detect if the centre of mass of the suspension arrangement load is positioned at a longitudinal position along the support line which is beyond a limit position based on a displacement of at least a portion of the main frame in relation to the main frame suspension arrangement.
33. The spreader according to claim 27, wherein the detector arrangement is configured to detect that said centre of mass is beyond the second support end based on a vertical displacement of the main frame relative to the main frame suspension arrangement at the first support end.
34. The spreader according to claim 33, wherein the detector arrangement comprises a first sensor adjacent to the first support end, the first sensor being configured to detect said vertical displacement of the main frame relative to the main frame suspension arrangement at the first support end.
35. The spreader according to claim 27, wherein the detector arrangement is configured to detect that said centre of mass is beyond the first support end based on a vertical displacement of the main frame relative to the main frame suspension arrangement at the second support end.
36. The spreader according to claim 33, wherein the detector arrangement comprises a first sensor adjacent to the first support end, the first sensor being configured to detect said vertical displacement of the main frame relative to the main frame suspension arrangement at the first support end, and to detect that said center of mass is beyond the first support end based on a vertical displacement of the main frame relative to the main frame suspension arrangement at the second support end, and the detector arrangement further comprises a second sensor adjacent to the second support end, the second sensor being configured to detect said vertical displacement of the main frame relative to the main frame suspension arrangement at the second support end.
37. The spreader according to claim 27, wherein the detector arrangement is configured to detect a vertical displacement of the main frame relative to the main frame suspension arrangement at least at two longitudinally separated positions.
38. The spreader according to claim 27, wherein the main frame suspension arrangement is configured to permit a vertical play of the main frame, at the first support end and the second support end, of less than 300 mm.
39. The spreader according to claim 27, wherein a downwards-facing surface of the main frame slidably rests on an upwards-facing surface of the main frame suspension arrangement to enable a longitudinal translation between the main frame and the main frame suspension arrangement.
40. The spreader according to claim 27, wherein the main frame comprises a pair of opposite outer side wall faces, each outer side wall face provided with a respective side-shift rail protruding therefrom and extending along said longitudinal axis, each side-shift rail resting on a respective vertical support of said main frame suspension arrangement so as to allow moving the main frame on said vertical supports along said longitudinal axis.
41. The spreader according to claim 27, wherein the support line is defined by a slide pad arrangement comprising at least one slide pad.
42. The spreader according to claim 27, wherein the first container connector arrangement comprises a first travelling beam, and the second container connector arrangement comprises a second travelling beam, wherein a proximal end of the first travelling beam is guided in the main frame to be telescopically extendable from the main frame in a first direction along said longitudinal axis, and a distal end of the first travelling beam is configured to engage with a first end of said transport container, and wherein a proximal end of the second travelling beam is guided in the main frame to be telescopically extendable from the main frame in a second direction along said longitudinal axis, and a distal end of the second travelling beam is configured to engage with a second end of said transport container.
43. The spreader according to claim 27, wherein each of said first and second container connector arrangements comprises a respective transversal beam extending in a direction transversal to the longitudinal axis, each of said transversal beams being provided with two respective lifting casting connectors separated along said transversal direction, for connecting to two lifting castings of said transport container.
44. The spreader according to claim 27, wherein the detector arrangement is configured to generate, based on said detection, an electronic indication signal to a control system or an operator of the spreader.
45. The spreader according to claim 27, wherein the detector arrangement comprises at least one actuator for powered pile slope, wherein the detection is based on a detected load on said at least one actuator.
46. The spreader according to claim 27, further comprising a crane connection interface comprising a crane bracket, the crane connection interface enabling the spreader to be rigidly connected to a crane arm or boom of e.g. a vehicle.
47. A container handling equipment comprising a spreader according to claim 27, the container handling equipment comprising a control system configured to, based on said detection, impose a control constraint limiting a set of permissible operations of the container handling equipment.
48. The container handling equipment according to claim 47, wherein the spreader comprises a rotator configured to rotate the main frame about a substantially vertical rotation axis perpendicular to the longitudinal axis, wherein said control system is configured to, based on a detected position of said centre of mass, brake or block a rotation of the main frame via said rotator, and/or impose a control constraint limiting a possibility to tilt the rotator about an axis parallel to the longitudinal axis.
49. A method of lifting a transport container using a spreader rigidly connected to a crane arm or boom, the method comprising: positioning a main frame at a longitudinal position along a main frame suspension arrangement; attaching container connector arrangements of the spreader at two longitudinal ends of said container; initiating a lift of said container by lifting said spreader; and detecting whether a longitudinal position of a centre of mass of a load carried by the main frame suspension arrangement is beyond a limit position.
50. The method of claim 49, comprising: detecting a longitudinal eccentricity of a centre of mass of the container; and based on the detected eccentricity, moving the centre of mass of the container sideways, towards a longitudinal centre of the main frame suspension arrangement, by moving the main frame sideways.
51. A spreader for lifting a transport container, the spreader comprising a main frame having a first end and a second end, and extending along a longitudinal axis between said first end and said second end, the first end being provided with a first container connector arrangement and the second end being provided with a second container connector arrangement, each of said first and second container connector arrangements comprising at least one respective lifting casting connector configured to engage with a lifting casting of a transport container; a main frame suspension arrangement, wherein the main frame is translatably suspended in said main frame suspension arrangement to enable translation along said longitudinal axis, wherein the main frame is configured to be vertically supported by the main frame suspension arrangement along a support line extending between a first support end and a second support end, such that the main frame carries the weight of a suspension arrangement load comprising the main frame, the container connector arrangements, and any container attached to the container connector arrangements; and, a detector arrangement configured to detect a vertical displacement of the main frame relative to the main frame suspension arrangement at least at two longitudinally separated positions.
52. A method of lifting a transport container using a spreader comprising a main frame extending along a longitudinal axis, the main frame being suspended in a main frame suspension arrangement, the method comprising: lowering the spreader onto the container; and detecting a vertical displacement of the main frame relative to the main frame suspension arrangement at least at two longitudinally separated positions.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the present invention, with reference to the appended drawings, where the same reference numerals will be used for similar elements, wherein:
[0034] FIG. 1 is an illustration in perspective of an intermodal transport container;
[0035] FIG. 2 is an illustration in perspective of a top lifting casting of the intermodal transport container of FIG. 1;
[0036] FIG. 3 is an orthographic projection of a spreader according to a first embodiment;
[0037] FIG. 4A is a schematic illustration of the spreader of FIG. 3 as seen from below, when in a longitudinally retracted position;
[0038] FIG. 4B is a schematic illustration of the spreader of FIG. 3 as seen from below, when in a longitudinally extended position;
[0039] FIG. 5 is a side view of a reach stacker carrying the spreader of FIG. 3;
[0040] FIG. 6 illustrates a cross-section of a main frame and a main frame suspension arrangement of the spreader of FIG. 3, the cross-section being taken along the plane VI-VI of FIG. 3;
[0041] FIG. 7A illustrates a cross-section of the main frame suspension arrangement and a side-shift rail of the main frame of the spreader of FIG. 3 in relation to a detector arrangement according to a first embodiment, the cross-section being taken along the plane VII-VII of FIG. 6, wherein the main frame and the main frame suspension arrangement are in a first mutual relationship;
[0042] FIG. 7B corresponds to the view of FIG. 7A, wherein the main frame and the main frame suspension arrangement are in a second mutual relationship;
[0043] FIG. 7C corresponds to the view of FIG. 7A, wherein the main frame and the main frame suspension arrangement are in a third mutual relationship;
[0044] FIG. 7D corresponds to the view of FIG. 7A, wherein the main frame and the main frame suspension arrangement are in a fourth mutual relationship;
[0045] FIG. 8 illustrates a cross-section of the main frame suspension arrangement and a side-shift rail of the main frame of the spreader of FIG. 3 in relation to a detector arrangement according to a second embodiment, the cross-section corresponding to that taken along the plane VII-VII of FIG. 6, mutatis mutandis, wherein the main frame and the main frame suspension arrangement are in a mutual relationship corresponding to the first mutual relationship of FIG. 7A;
[0046] FIG. 9 is a perspective view, as seen obliquely from below, of a lifting casting connector of the spreader of FIG. 3;
[0047] FIG. 10 is a perspective view, as seen obliquely from above, of a male locking insert of the lifting casting connector of FIG. 9;
[0048] FIG. 11A is a side view illustrating the spreader of FIG. 3 and the container of FIG. 1 prior to connection;
[0049] FIG. 11B corresponds to the view of FIG. 11A, illustrating the spreader and the container after connection, wherein the main frame and the main frame suspension arrangement of the spreader are in a first mutual relationship;
[0050] FIG. 11C corresponds to the view of FIG. 11B, wherein the main frame and the main frame suspension arrangement of the spreader are in a second mutual relationship;
[0051] FIG. 12 is a side view illustrating another embodiment of a spreader connected to the container of FIG. 1;
[0052] FIG. 13 is a flow chart illustrating a method of lifting a container according to a first embodiment;
[0053] FIG. 14 is a flow chart illustrating a method of lifting a container according to a second embodiment; and
[0054] FIG. 15 is a flow chart illustrating a method of lifting a container according to a third embodiment;
[0055] All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the embodiments, wherein other parts may be omitted.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0056] FIG. 1 schematically illustrates an intermodal container 10 according to the above-mentioned ISO standards. The container 10, which for clarity is illustrated transparent, has a top face 10a, a first longitudinal side 10b, and a first short side or gable side 10c. The container also has a bottom face 10d, a second longitudinal side, and a second gable side 10e, which are located parallel and opposite the top face 10a, first longitudinal side 10b, and first gable side 10c, respectively. Each corner of the container 10 is provided with a respective lifting casting for attaching a respective lifting casting connector, for the purpose of facilitating the handling of the container 10, and for locking the container 10 to other containers or to the deck of a freight ship. Hence, the container top corners which define the corners of the top face 10a are provided with two lifting castings 12a at a first longitudinal end 14a of the container 10, and two lifting castings 12b at a second longitudinal end 14b of the container 10. Similarly, the container bottom corners are provided with four bottom lifting castings 15a, 15b at the four corners of the bottom face.
[0057] FIG. 1 also illustrates the container 10 arranged in a cartesian coordinate system, wherein the bottom face 10d of the container 10 is in the x-y plane, the longitudinal sides 10b of the container 10 are arranged along the x-z plane, and the gable sides 10c, 10e of the container 10 are arranged along the y-z plane. The rotation directions of a container 10 are typically given by reference to the directions of rotation of a container arranged on a cargo ship. Containers 10 arranged on a cargo ship are aligned with the cargo ship having the longitudinal sides 10b along the length of the cargo ship. The rotational motions of the container may therefore be defined by reference to the motions of the cargo ship, i.e. list, trim and skew. List is rotation about the x-axis, and is sometimes also referred to as tilt. Trim is rotation about the y-axis; herein, trim may also be referred to as sideways leaning of the container 10. Skew is rotation about the z-axis.
[0058] FIG. 2 illustrates one of the top lifting castings 12b in greater detail, in the same perspective as that of FIG. 1. It is provided with a top face lock opening 18, a longitudinal side lock opening 20, and a gable lock opening 22, each of which is configured to receive and engage with a male insert of a lifting casting connector, such as a lifting hook or a twist-lock. It will be appreciated that all top lifting castings 12a, 12b may be identical, albeit in a mirror configuration.
[0059] FIG. 3 illustrates a top-lift spreader 24 for handling an intermodal transport container according to the above-mentioned ISO standards. The spreader 24 comprises a main frame 26 extending along a longitudinal axis L between a first end 26a and a second end 26b. The first end 26a carries a first container connector arrangement 28a configured to be connected to the first end 14a of the container (FIG. 1), and the second end 26b carries a second container connector arrangement 28b configured to be connected to the second end 14b of the container (FIG. 1).
[0060] The spreader 24 further comprises a main frame carrier 30 comprising a crane bracket 32, which is configured to be connected to a crane (not illustrated) such as a telescopic boom crane or a wire crane. The crane bracket 32 is connectable to the crane to enable tilting the container about a horizontal pivot axis A1, extending along the longitudinal axis L, for changing the tilt of the container 10 (FIG. 1). For the purpose, a pair of hydraulic tilt cylinders 33 are likewise connectable to the crane. The main frame carrier 30 further comprises a rotator 34 enabling rotation of the main frame 26, and thereby any container(s) 10 held by the spreader 24, in relation to the crane bracket 32 about a substantially vertical rotation axis A2 for changing the skew of the container. The main frame carrier 30 also comprises a main frame suspension arrangement 36 enabling translation of the main frame 26 relative to the main frame carrier 30 along the longitudinal axis L. The main frame suspension arrangement 36 thereby carries the weight of a suspension arrangement load comprising the main frame 26, the container connector arrangements 28a, 28b, and any container(s) 10 attached to the container connector arrangements 28a, 28b. A side-shift mechanism 37, configured as a hydraulic cylinder extending along the main frame 26, is connected to the main frame 26 as well as to the main frame suspension arrangement 36. The side-shift mechanism 37 enables moving the main frame 26 relative to the main frame suspension arrangement 36 along the longitudinal axis L. The side-shift mechanism 37 also comprises a side-shift sensor (not illustrated) enabling determining the mutual positional relationship between the main frame suspension arrangement 36 and the main frame 26. The side-shift sensor may be arranged within the hydraulic cylinder as such, or be provided as a separate sensor.
[0061] FIGS. 4A and 4B illustrate the spreader 24 in a highly schematic manner, and as seen from below. The first container connector arrangement 28a comprises a first travelling beam 38a guided in first travelling beam guide configured as a sleeve 27a within the main frame 26. Similarly, the second container connector arrangement 28b comprises a second travelling beam 38b guided in second travelling beam guide configured as a sleeve 27b within the main frame 26. The travelling beams 38a, 38b are telescopically extendable between a retracted position (FIG. 4A) for connecting the spreader 24 to a 20-foot container, and an extended position (FIG. 4B) for connecting the spreader 24 to a 40-foot container. A proximal end 40a of the first travelling beam 38a is guided in the main frame 26 to be telescopically extendable from the main frame 26 in a first extension direction E1 along the longitudinal axis L, and a distal end 42a of the first travelling beam 38a is provided with a respective first transversal beam 44a extending in a transversal direction T substantially perpendicular to the longitudinal axis L. The first container connector arrangement 28a further comprises a first pair of lifting casting connectors configured as twist-locks 46a arranged at opposite ends of the first transversal beam 44a, which first pair of twist-locks 46a are connectable to the top face lock openings 18 (FIG. 2) of the top lifting castings 12a of the container's 10 first longitudinal end 14a.
[0062] Similarly, a proximal end 40b of the second travelling beam 38b is guided in the main frame 26 to be telescopically extendable from the main frame 26 in a second extension direction E2 opposite to the first extension direction along the longitudinal axis L, and a distal end 42b of the second travelling beam 38b is provided with a respective second transversal beam 44b extending along the transversal direction T. The second container connector arrangement 28b comprises a second pair of lifting casting connectors configured as twist-locks 46b arranged at opposite ends of the second transversal beam 44b, which second pair of twist-locks 46b are connectable to the top face lock openings 18 (FIG. 2) of the top lifting castings 12b of the container's 10 second longitudinal end 14b. For the sake of clarity, it is pointed out that FIG. 3 illustrates the spreader 24 with the travelling beams 38a, 38b in the retracted position, such that they are hid within the main frame 26.
[0063] FIG. 5 illustrates the spreader 24 attached to a telescopic boom crane 48 of a truck 50, to form a reach stacker 52. FIG. 5 illustrates the reach stacker 52 with a container 10 attached to the spreader 24. The truck 50 is also provided with a control system 54, comprising electronics and/or computer program instructions for controlling the truck 50 as well as the crane 48 and the spreader 24.
[0064] FIG. 6 highly schematically illustrates the main frame 26 and the main frame suspension arrangement 36 in a section along a section plane VI-VI (FIG. 3) perpendicular to the longitudinal axis L. The main frame comprises a pair of opposite outer side wall faces 56. A respective side-shift rail 58 is welded to the outer face of each side wall 56, the side-shift rails 58 protruding from the side walls 56 and extending along the longitudinal axis L (FIG. 3). Each side-shift rail 58 is vertically supported by and slidingly rests on a respective vertical support 60 of the main frame suspension arrangement 36, to allow sliding the main frame on the vertical supports 60 along said longitudinal axis L. The vertical supports 60 are provided with slide pads 64, which may be made of e.g. plastic such as polyurethane, for reducing the friction for sliding the main frame 26 along the main frame suspension arrangement 36. The slide pads 64 also define a pair of opposite side supports 62 facing the respective outer side wall faces 56, for guiding the main frame 26 along the longitudinal axis L. FIG. 6 also illustrates the travelling beams 38a, 38b within their respective travelling beam guides 27a, 27b. Friction-reducing slide pads 66 are arranged around the circumferences of the travelling beams 38a, 38b.
[0065] FIG. 7A illustrates a side-shift rail 58 and the main frame suspension arrangement 36 as seen in the section VII-VII of FIG. 6. The downwards-facing surface of the side-shift rail 58 movably rests upon the upwards-facing surfaces of the slide pads 64 along a support line S extending between a first support end 68a and a second support end 68b. The main frame suspension arrangement 36 further comprises, at a distance D1 above the side-shift rail 58, a first upper limit stop 70a and a second upper limit stop 70b, which provides an upper limit for the side-shift rail 58 in case it loses contact with the slide pads 64. This may occur in situations which will be elucidated in the following. Each of the upper limit stops 70a, 70b is also provided with a respective side-shift rail detector 72a, 72b, configured to detect the presence of the side-shift rail 58, and to communicate respective sensor signals to the control system 54 (FIG. 5). Similar upper limit stops 72b′ and side-shift rail detectors 70b′ may optionally be provided at the opposite side of the main frame 26. The side-shift rail detectors 72a, 72b form a simple detector arrangement 72 capable of detecting if a centre of mass of the suspension arrangement load is positioned beyond any of the support ends 68a, 68b.
[0066] FIG. 7B illustrates a situation in which the centre of mass of the suspension arrangement load is positioned beyond the first support end 68a. In such a situation, the first support end 68a defines a fulcrum about which the suspension arrangement load, i.e. the main frame 26 (FIG. 3) together with any additional load carried by it, pivots. When the side-shift rail 58 reaches the second upper limit stop 70b, the presence of the side-shift rail 58 will be detected by the second side-shift rail detector 72b. The presence of the side-shift rail 58 at the second upper limit stop 70b, combined with non-presence of the side-shift rail 58 at the first upper limit stop 70a, indicates that the position of the suspension arrangement load's centre of mass is not between the first and second support ends 68a, 68b, but instead beyond the first support end 68a, as seen from a position between the support ends 68a, 68b.
[0067] In response to having detected the eccentric load situation of FIG. 7B, the control system 54 (FIG. 5) may impose a control constraint preventing e.g. side-shifting the main frame 26 (FIG. 3), thereby preventing friction wear between the second limit stop 70b and the upper face of the side-shift rail 58, and/or preventing further lifting of the container 10 (FIG. 5). The control system 54 may also be configured to operate a side-shift actuator to translate the main frame 26 relative to the main frame suspension arrangement 36 in a direction along the longitudinal axis L, to the right as seen in the view of FIG. 7B, thereby moving the longitudinal position of the suspension arrangement load's centre of gravity to a position between the support ends 68a, 68b. Still further, the control system 54 may be configured to brake or block a rotation of the main frame 26 via the rotator 34 (FIG. 3), and/or impose a control constraint limiting the possibility to tilt the rotator 34 about an axis parallel to the longitudinal axis L.
[0068] FIG. 7C illustrates a situation similar to that of FIG. 7B, though the centre of mass of the suspension arrangement load is instead positioned beyond the second support end 68b. In such a situation, the second support end 68b defines a fulcrum about which the suspension arrangement load pivots. When the side-shift rail 58 reaches the first upper limit stop 70a, the presence of the side-shift rail 58 will be detected by the first side-shift rail detector 72a. The presence of the side-shift rail 58 at the first upper limit stop 70a, combined with non-presence of the side-shift rail 58 at the second upper limit stop 70b, indicates that the position of the suspension arrangement load's centre of mass is beyond the second support end 68b, as seen from a position between the support ends 68a, 68b. The situation may be dealt with by the control system in a manner similar to that described with reference to FIG. 7B, mutatis mutandis.
[0069] As is apparent from FIGS. 7A-C, the detector arrangement comprising the side-shift rail detectors 72a, 72b is able to detect a change in the angle β formed between the main frame 26, in FIG. 7C represented by the side-shift rail 58, and the main frame suspension arrangement 36. The detector arrangement can also detect the direction of change of the angle R. The side-shift rail detectors 72a, 72b may also be configured to determine a shortest distance from the respective side-shift rail detector 72a, 72b to the side-shift rail 58, thereby enabling a determination of a magnitude of change of the angle R.
[0070] FIG. 7D illustrates a situation in which the side-shift rail 58 along its entire length has been raised above the support line S, indicating that the suspension arrangement load is no longer carried by the main frame suspension arrangement 36. The situation may be detected by both side-shift rail detectors 72a, 72b indicating to the control system 54 (FIG. 5) the presence of the side-shift rail 58. Such a situation may occur if the spreader is lowered until the main frame 26 rests upon a container 10, and the main frame suspension arrangement 36 is thereafter lowered even further. The control system 54 may respond to a detection of the illustrated situation by e.g. generating a signal to an operator or a control system to stop lowering the spreader 24, or to restrict the lowering speed.
[0071] FIG. 8 illustrates a schematically illustrates a detector arrangement 172 according to a second embodiment. Similar to the detector arrangement 72 of FIGS. 7A-7D, the detector arrangement 172 of FIG. 8 comprises two side-shift rail detectors 172a, 172b arranged adjacent to the respective support ends 68a, 68b of the support line S and configured to detect the presence of the side-shift rail 58. However, the detector arrangement 172 of FIG. 8 differs from the detector arrangement 72 of FIGS. 7A-7D in that the detectors 172a, 172b are arranged below the side-shift rail 58. Thereby, the detector arrangement 172 would detect e.g. the situation illustrated in FIG. 7B not by detecting the presence of the side-shift rail 58 at the second side-shift rail detector 72b (FIG. 7B), but by detecting the absence of the side-shift rail 58 at the second side-shift rail detector 172b.
[0072] FIG. 9 schematically illustrates a twist-lock 46b comprising a male locking insert 74 configured to be inserted into a top opening 18 (FIG. 2) of a respective container lifting casting 12b (FIG. 2). Once inside the lifting casting 12b, an end portion 76 of the male locking insert 74 is configured to be twisted 90° about a vertical axis R to a lock position, in which it engages with the lifting casting 12b. An abutment face 78 (hatched), flanking the male locking insert 74, corresponds to the size and shape of the top surface 19 (FIG. 2) of the lifting casting 12b, and is configured to rest thereupon once the spreader 24 (FIG. 3) has been lowered onto the container 10. A landing indicator has a vertically movable indicator body 80, a portion of which protrudes downwards from the abutment face 78. The landing indicator is configured to indicate when the upper surface 19 of the lifting casting 12b presses the indicator body 80 vertically into the abutment face 78 of the twist-lock 46b, and to notify the control system 54 (FIG. 5) of such an event.
[0073] The twist-lock 46b is further provided with a vertical load sensor 272b configured to measure the vertical load carried by the twist-lock 46b. FIG. 10 illustrates an example embodiment of the sensor 272b, according to which the vertical load sensor 272b (FIG. 9) is configured as a strain gauge 280 carried by the male locking insert 74. Similar vertical load sensors are provided on all four twist-locks 46a, 46b of the spreader 24 (FIG. 4A), such that the vertical load on each of the respective twist-locks 46a, 46b may be determined. Together with the longitudinal position of the main frame 26 relative to the main frame suspension arrangement 36, as determined by the side-shift sensor of the side-shift mechanism 37 (FIG. 3), the vertical load determined by the vertical load sensors 272b enables determining the position of the centre of mass of the suspension arrangement load. Such a determination may be made in a control system of the spreader 24 (FIG. 3) or any container handling equipment operating the spreader 24, such as the control system 54 (FIG. 5). Thereby, the side-shift sensor, the control system 54, and the vertical load sensors 272b together define, now with reference to FIG. 11A, a detector arrangement 272 configured to detect the position of the centre of mass of the suspension arrangement load along the support line S according to a third embodiment. In particular, the detector arrangement 272 enables determining whether the centre of mass is beyond a limit position along said support line S. FIGS. 11A-11C illustrate the operation of the detector arrangement 272 according to the third embodiment.
[0074] Starting with the situation of FIG. 11A, the spreader 24 is lowered onto a container 10 for connection thereto via container connector arrangements 28a-b.
[0075] In the situation of FIG. 11B, the spreader 24 has been connected to the container 10, and initiates a lift in the direction indicated by an arrow. The total vertical suspension arrangement load, carried by the main frame suspension arrangement 36, is the sum of the mass of the container 10, the main frame 26, and the container connector arrangements 28a-b. In the view of FIG. 11B, the centre of mass of the container is indicated by Mc, and the weight of the container 10, i.e. the gravitational force on the container 10, is indicated by arrow Gc. Similarly, the centre of mass of the main frame 26 and container connector arrangements 28a-b is indicated by Mf, and the weight of the main frame 26 and container connector arrangements 28a-b is indicated by arrow Gf. As is apparent from the position of the container's centre of mass Mc, the container weight Gc is eccentric relative to the container's 10 geometric centre along the longitudinal axis L. The total vertical load Gt on the main frame suspension arrangement 36, formed by the sum of the container, main frame, and container connector arrangement weights Gc, Gf, is also eccentric along the longitudinal axis L relative to the main frame suspension arrangement 36, and will generate a torque on the main frame suspension arrangement 36, which torque may have a negative impact on the handling of the container 10.
[0076] Based on the vertical loads determined by the respective vertical load sensors 272b (FIG. 9) of the container connector arrangements 28a-b, in combination with the side-shift position as determined by the side-shift mechanism 37 (FIG. 3), and a priori knowledge of the centre of mass Mf and weight Gf of the main frame 26 and container connector arrangements 28a-b, the longitudinal position relative to the main frame suspension arrangement 36 of the weight Gt and centre of mass Mt of the total suspension arrangement load may be determined, for example in the control system 54 (FIG. 5). The control system 54 may also make a determination that the centre of mass Mt is beyond a limit position P, and in response thereto, side-shift the main frame 26. The limit position P may be a longitudinal distance from the longitudinal centre C of the main frame suspension arrangement 36, which longitudinal distance may be set in the control system 54 (FIG. 5). Thereby, the embodiment described with reference to FIGS. 11A-11C differs from that described with reference to FIGS. 7A-D in that the limit position P may be freely set, and is not necessarily located to a support end 68a-b (FIG. 7A).
[0077] In the situation of FIG. 11C, the control system 54 has operated, based on the longitudinal position of the total suspension arrangement load Gt determined in the situation of FIG. 11B, the side-shift mechanism 37 (FIG. 3) to move the main frame 26 in the direction of the horizontal arrow H along the longitudinal axis L to the illustrated position, in which the suspension arrangement load Gt is now centred below the main frame suspension arrangement 36.
[0078] FIG. 12 illustrates an embodiment of a spreader 24 provided with powered pile slope actuators 90, which actuators 90 are configured as hydraulic cylinders. The powered pile slope actuators 90 are controlled by the control system 54, and enable sideways leaning of the container 10 about a pivot 92. A difference in hydraulic pressure between the powered pile slope actuators 90, when the container is held horizontally, indicates an eccentric suspension arrangement load Gt, which indication may be used in accordance with the teachings herein. Hence, the powered pile slope actuators 90 may form part of a detector arrangement 372 configured to detect if the centre of mass Mt of the suspension arrangement load is positioned at a longitudinal position which is beyond a limit position. A single, double-acting hydraulic cylinder would enable the same functionality as the two actuators 90 of FIG. 12.
[0079] The flow chart of FIG. 13 illustrates a method of lifting a container using a spreader 24 described hereinabove, the method enabling the detection of potentially dangerous situations posed by an eccentric load. The method comprises the steps [0080] 1301: positioning the main frame 26 at a longitudinal position along the main frame suspension arrangement 36; [0081] 1302: attaching the container connector arrangements 28a, 28b of the spreader at two longitudinal ends 14a, 14b of the container 10; [0082] 1303: initiating a lift of the container 10 by lifting the spreader 24; and [0083] 1304: detecting whether a longitudinal position of a centre of mass of a load Gt carried by the main frame suspension arrangement 36 is beyond a limit position.
[0084] The flow chart of FIG. 14 illustrates a second method of lifting a container using a spreader 24 described hereinabove, the method mitigating any potentially dangerous consequences of eccentrically loaded transport containers. The method comprises the steps [0085] 1401: attaching container connector arrangements 28a, 28b, carried by the main frame 26, at two longitudinal ends 14a, 14b of the container 10; [0086] 1402: initiating a lift of the container 10 by lifting the spreader 24; [0087] 1403: detecting a longitudinal eccentricity of a centre of mass Mc of the container 10; and [0088] 1404: based on the detected eccentricity, moving the centre of mass Mc of the container 10 sideways, towards a longitudinal centre of the main frame suspension arrangement 36, by moving the main frame 26 sideways.
[0089] The flow chart of FIG. 15 illustrates a third method of lifting a container using a spreader 24 described hereinabove, the method enabling detecting when the spreader 24 has landed on the container 10. The method comprises the steps [0090] 1501: lowering the spreader onto the container 10; and [0091] 1502: detecting a vertical displacement of the main frame 26 relative to the main frame suspension arrangement 36 at least at two longitudinally separated positions.
[0092] The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. By way of example, the invention is applicable to spreaders configured to engage with, and lift, other containers than standardized intermodal transport containers. Container connector arrangements may be of types different from twist-locks, such as lifting hooks and grapple arms. Even though the invention has been described with reference to top-lift spreaders, the teachings herein are also applicable to side-lift spreaders configured to engage with only a single longitudinal side of a transport container.
[0093] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality.
