FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a hook-lift for loading a pay load carrier to a vehicle according to the introductory portion of claim 1 and to a vehicle including such a load handling structure. Such a hook-lift and such a vehicle are known from EP-A-I 053 909.

The purpose of a hook-lift is loading and unloading a payload carrier, over the rear of a vehicle, such as a flatbed or pick-up truck or a trailer. The payload carrier has a guide structure along its underside suitable to run over the rear end of the vehicle, for instance over rollers that are rotatably mounted to the vehicle chassis, during the loading and unloading operations. The payload carrier may for instance be a flat frame or a container at the front end of which a bar is provided that is engaged by the hook-lift.

Construction of such hook-lifts is laborious and such constructions are of a substantial weight, whereas it is a general objective in vehicle design to reduce weight.

In NL-C-I 021 023, it is suggested to reduce costs of manufacturing and assembly of the hydraulic system and to reduce weight by building up a hook-lift system on the basis of extruded aluminium sections in which the hydraulic components are integral with the frame, the frame consisting of singular, i.e. non-assembled beams.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a further solution to make manufacturing of a hook-lift less laborious and to provide a more lightweight construction.

According to the present invention, this object is achieved by providing a hook-lift according to claim 1. The invention may also be embodied in a vehicle according to claim 12.

By providing that the proximal part comprises at least one extruded aluminium section extending in longitudinal direction of the proximal part, the connection of at least a number of fittings, such a hooks, hinge members

and arm actuators, to the hook-lift arm can be simplified and the weight of the hook lift arm is reduced, which is advantageous for lowering the overall center of gravity and for reducing mass displacement and loads exerted due to movements of the hook-lift arm itself when the hook -lift arm is moved during operation.

Particular embodiments of aspects of the invention are set forth in the dependent claims.

Further aspects, effects and details of the invention are set forth in the detailed description with reference to examples of which some are shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figs. IA- IF form a sequence of schematic views showing unloading of a p ay load carrier from an example of a vehicle according to the invention;

Fig. 2 is an example of a hook-lift for use as part of the vehicle shown in Figs. 1A-1F;

Fig. 3 is a view in cross -section along the line III -III in Fig. 4 through a proximal part of a hook-lift arm of the hook-lift shown in Fig. 2;

Fig. 4 is a side-view in cross-section of a portion of the proximal part of the hook-lift arm of the hook-lift shown in Figs. 2 and 3; Fig. 5 is a perspective view of mutually adjacent portions of the proximal part and of a distal part of the hook-lift arm of the hook-lift shown in Fig. 2;

Fig. 6 is a partially cut-away view along lines VI-VI and VT-VI' in Fig. 7 of the hook-lift arm of the hook-lift shown in Figs. 2-5; Fig. 7 is a view in cross-section along the line VII-VII in Fig. 6 of the hook-lift arm of the hook-lift shown in Figs. 2-6;

Fig. 8 is a view in cross-section of a longitudinal beam of the hook-lift shown in Fig. 2-7 with an enlarged view of a corner portion; and

Fig. 9 is a cross -sectional view of a pivotable connection between a frame and an hydraulic operating member of the hook-lift shown in Figs. 2-8.

MODES FOR CARRYING OUT THE INVENTION

In Figs. IA- IF an example of a vehicle 1 according to the present invention is shown. The vehicle comprises a cab 2 mounted on a chassis 3, which is supported on wheels 4-6. The vehicle also includes a hook-lift 7 for

loading and unloading payload bodies 8, such as open or closed containers or flatracks. The hook-lift 7 is shown in more detail in Fig. 2. A base frame 9 of the hook-lift 7 is mounted to the chassis 3. The base frame 9 may is mounted fixedly to the chassis 3, but may in principle also be provided as an integral part of the chassis.

A hook-lift arm 10 is mounted pivotably to the base frame 9 and is pivotable between a transport position (Fig. IA) and a load engagement position (Fig. IF) in which the arm can engage a payload carrier or disengage from a payload carrier. The hook-lift arm 10 is mainly constituted by a proximal part 11 and a distal part 12 projecting perpendicularly from the proximal part 11. Depending on the design of the vehicle and of the payload bodies, other angles between the proximal and distal parts of the hook -lift arm are in principle also possible. The proximal part 11 extends along the base frame 9, approximately parallel to the base frame 9 and the distal part 12 projects upwardly relative to the base frame 9 when the hook-lift arm 10 is in the transport position. When the hook-lift arm 10 is in the load engagement position, the proximal part 11 extends upwardly from the base frame 9. According to the present example, the distal part moreover projects rearwardly beyond the rear end of the base frame 9 to allow engagement to and disengagement from a load carrier in a position spaced behind the rear end of the vehicle 1.

For pivoting the hook-lift arm 10 relative to the base frame 9 between the transport and load engagement positions, the hook-lift 7 is equipped with an operating structure 13 connected between the base frame 9 and the hook- lift arm 10. According to the present example, a pair of hydraulic cylinders 13 forms the operating structure.

A support 14 is arranged at a rear end of the base frame 9 for supporting guides 15 (see Fig. 1C) extending longitudinally along the bottom of a payload carrier 8 and for allowing the guides 15 to be displaced in longitudinal direction over the support 14.

For engaging to a load 8 and disengaging from a load 8, the hook-lift arm 10 is equipped with a hook 16. It is observed that, within the framework of the present invention, also other hooks, including any device for selectively engaging to and disengaging from a load suitable for co-operation therewith may be employed, such as a coupling with one or more locking members or other member or members for providing form-determined engagement.

The proximal part 11 of the hook-lift arm 10 is formed by an inner section 17 telescopically received in an outer section 18. An operating member in the form of a hydraulic cylinder 24 extends inside the proximal part 11 and is connected to the inner and outer sections 17, 18 for operating telescopic extension and retraction of the proximal part 11. As the operating member 13, the operating member 24 may in principle be provided in alternative forms, such as in the form of a spindle, a rack and pinion or a cable drive. The outer section 18 is hinged to the base frame 9 via two flange bodies 19 to which the hydraulic cylinders 13 are hinged. The flange bodies 19 are hinged to inner longitudinal beams 20 of the base frame 9. The flanged bodies 19 are welded to the outer section 18.

The inner longitudinal beams 19 are hinged to outer longitudinal beams 21 at hinges 22 and are provided with hooks 23 for engaging a load carrier. The unloading movement of the load handling system is such as to move the hook-lift arm 10 from the transport position shown in fig. IA, through an intermediate position shown in Fig. IB to a final position shown in Fig. IF. The main arm 10 is pivoted by the double acting (pushing and pulling) hydraulic cylinder and piston arrangements 13. When a payload carrier 8 is loaded on the hook-lift 7, the hook 16 is engaged to a bar of the payload carrier 8 and the arm 10 keeps the payload carrier 8 in position when the arm 10 is in its transport position. Preferably further security lockings are provided, as is known as such, to ensure safe immobilization of the payload carrier 8 on the hook -lift 7 for instance in the event of a failure in the hydraulic system.

For unloading the payload carrier 8, the movement path of the hook 16 is first linear in rearward direction from a position shown in Fig. IA to a position shown in Fig. IB. To this end, the operating member 24 in the proximal part 11 of the hook-lift arm 10 is operated for causing the inner section 17 to telescopically move into the outer section 18. This causes the load carrier 8 to be shifted backward and the hooks 23 to disengage from the load carrier 8.

Next, the operating structure 13 is expanded, causing the hook-lift arm 10 to be pivoted upwardly from the base frame 9. Such movement is on the one hand allowed, since the hooks 23 are unhooked from the load carrier and on the other hand facilitated by the counter weight formed by a portion of the load carrier 8 projecting backward from the support 14. The pivoting

movement of the load carrier 8 and of the hook-lift arm 10 is in a common generally -vertically plane since the axis about which the hook -lift armlO is pivotable is oriented horizontally and perpendicular to the longitudinal direction of the vehicle 1. As the hook-lift arm 10 is pivoted upwardly from the base frame 9, the load carrier 8 is lifted at its front end and tilted about the support 14. Once the load carrier 8 hits the ground (Fig. 1C) and the pivoting movement of the hook-lift arm 10 is continued, the front end of the load carrier 8 is lifted from the support 14 (Fig. ID), the load carrier 8 is displaced backwards from the vehicle 1 (Fig. IE) and finally positioned on the ground in a position spaced behind the vehicle 1 (Fig. IF). Then, pivoting the hook -lift arm 10 further easily disengages the hook 16.

If the hydraulic cylinder 24 in the proximal part 11 of the hook-lift arm 10 are not extended and only the hydraulic cylinders 13 arranged between the proximal part 11 of the hook-lift arm 10 and the base frame 9 are extended, the hooks 23 remain in engagement with the load carrier 8, thereby preventing the hook-lift arm 10 from pivoting relative to the inner longitudinal beams 19. This causes the inner longitudinal beams 19 to pivot with the load carrier 8 about the hinge 22 and allows to tilt the load carrier 8 without unloading it from the hook-lift 7, for instance for dumping material out of the load carrier 8.

The proximal part 11 of the hook-lift arm 10 includes an extruded aluminium section formed by the inner section 17 extending in longitudinal direction of the proximal part 11. As is best shown in Figs. 3-7, the inner section 17 has a cross-section shaped such that surfaces 25, 26 abut guide bodies 27, 30 from two sides and lock-up the guide bodies 27 between the inner section 17 and inner surfaces 28, 29 of the outer section 18 against displacement in directions transverse to the sections 17, 18. According to the present example, both the inner section 17 and the outer section 18 are extruded aluminium sections, so that accuracy of fit of the guide bodies 27 between the inner and outer sections 17 and 18 is controlled in a simple manner. The guide bodies 27 are fixed to the outer section 18 adjacent an end of the outer section 18 extending around the inner section 17 by fasteners 51 re leasable from the outside of the outer section 18. This allows the guide bodies 27 to be replaced without removing the inner section 17 from the outer section 30. According to the present example, the fasteners are 51 are bolts having countersunk heads. The guide bodies 30 are fixed to the inner section

18 adjacent an end of the inner section 17 inside the outer section 18 via a guide body retention member 52 that is fastened to a head end of the inner section 17. Because the guide bodies 30 of the second group are fastened to a head end of the inner section 17, these guide bodies 30 can be replaced easily without removing the inner section 17 from the outer section 18 and the fasteners engaging a head end of the inner section 17 are easily accessible via an open end of the outer section 18, in particular when the inner section 17 is retracted in the outer section 18. According to the present example, the guide body retention member 52 is a plate by which the guide members 30 are held. The plate 52 is bolted by bolts 53 threaded into a head end of the inner section 17.

The loads exerted transverse to the sections and in particular the relatively large vertical loads that occur in operation are effectively transferred by the guide bodies 27, 30 vertically contacting the sections 17, 18 in areas closely adjacent vertical walls 29, 51 of the sections 17, 18, so that deformation of the walls of sections 17, 18 remains limited.

The guide bodies are easily mountable, since the inner and outer sections 17, 18 are shaped to keep the guide bodies 27, 30 in place transversally to the sections 17, 18 and the guide bodies 27, 30 only need to be fixed against displacement in longitudinal direction, in which direction the forces exerted onto the guide bodies are relatively small. When worn, the guide bodies 27, 30 can easily be replaced.

The locking of the guide bodies 27, 30 against displacement in directions transverse to the sections 17, 18 is achieved in a particularly simple manner, because a gap 31 between the outer member 18 and the inner member 17 is left, and the cross-section of that gap 31 has areas wider than adjacent areas, the guide bodies 27, 30 being locked in the wide areas.

The cross-section of the inner member 17 has walls 32 having a central portion 33 extending closer to the outer member 18 than lateral portions 34 of those walls 32. The guide members 27, 30 are locked-in in directions transverse to the sections 17, 18 between mutually facing outer surfaces of the lateral portions 34 and inner surfaces 28 of the outer section 18. The central wall portions 33 extend partially between the guide members 27, 30 and prevents the guide members 27, 30 from laterally moving away from a lateral wall 51 of the outer section 18. This allows the guide members 27, 30 to be of a very simple design. The central portions 33 of the inner section 17 furthermore forms a reinforcement of the inner section 17

increasing stiffness and resistance against bending loads and provides a wall portion of sufficient thickness to receive the bolts 53 threaded into a head end of the inner section 17.

According to the present example, two sets of four guide bodies 27, 30 are arranged between the inner section and the outer section 18. Each of the guide bodies 27, 30 is rectangular and each one of the guide bodies 27, 30 is retained in a corner of the outer section 18 by surfaces 25, 26 of the inner section 17 facing in different directions towards inner surfaces 28 and, respectively, 29 of the outer section 18. The base frame 9 includes longitudinal aluminium sections 19, 21. As is best seen in Fig. 8, according to the present example, the outer ones 21 of these sections 19, 21 each have two T-slots 36 having an opening 37 facing to the outside of the frame 9 and two T-slots 38 having an opening 39 facing to the inside of the frame 9. Such T-slots facilitate mounting of fittings, such as the fitting 40 shown in Fig. 8, using bolts 41 of which heads are retained in the wide inner portions of the T-slots 36, 38. It is observed that this effect may also be achieved in a hook-lift of which the proximal part of the hook-lift arm does not comprise at least one extruded aluminium section extending in longitudinal direction of the proximal part. Instead of T-shaped slots, also other slots with a lateral opening narrower than a deeper area of the slot, such as a dovetail slot or an L-shaped slot may be provided, although the wide portion of the slot preferably projects beyond the lateral opening in two opposite directions. Since the sections 21 in which the slots 36, 38 are provided are of extruded material, the slots can be obtained easily during extrusion.

Referring in particular to Figs. 5-7, according to the present example, also the distal part 12 of the hook-lift arm 10 includes an extruded aluminium section 43 extending in longitudinal direction of the distal part 12. This section 43 is welded to an extruded aluminium section 17 of the proximal part 11. These welded sections 17, 43 have cross -sections of which one fits closely inside the other in horizontal direction. Edges 44 of vertical wall sections 45 of the section 43 of the distal part 12 extend along outer surfaces 46 of vertical wall sections of the section 17 of the proximal part 11. Since the weld 47 extends in a gutter between the edges 44 of the vertical wall sections 45 and adjacent zones of the outer surfaces 46 of the vertical wall sections of the other one of the sections, there is no need for special machining of the sections 17, 43 before the sections are welded together.

At the outside head end of the distal part 12, a weld 54 extends in a gutter between a head end of an outer wall 55 of the distal part and a head end of a bottom wall 56 of the inner section 17 of the proximal part 11. The outside head end of the distal part 12, is cut off at a more blunt angle than the angle to the longitudinal direction of the distal part 12 at which the edges 44 are oriented, so that a wide gutter is obtained that is easily and reliably filled during welding. A further weld 57 extends in a gutter formed by an inside corner between the proximal part 11 and the distal part 12.

The hook-lift arm 10 is further equipped with a hook member 16 that is mounted to the extruded aluminium section 43 by two connection bars 48, 49 extending between and mutually connecting opposite walls 45 of the aluminium section 43 and carrying the hook member 16 in apposition between these opposite walls 45. This connection is simple to manufacture and provides an evenly distributed load transfer from the hook member 16 to the section 43.

Lateral loads exerted to the hook-lift arm 10 should preferably remain limited, because hook-lift arms are primarily designed to resist loads in a vertical plane. To reduce lateral loads exerted onto the arm 10, for instance when the hook member 16 engages a load carrier from a not fully aligned position, a positioning structure 50 of elastic material, such as a rubber or a plastic, is arranged and extends between the hook member 16 and the opposite walls 45 of the aluminium section 43. The hook member 16 is mounted to the bars 48, 49 with a sliding fit and the elastic material resiliently maintains the hook member 16 in a position between the opposite walls 45. Since the hook member 16 is plate -shaped, it has a large resistance against load in the plane in which the plate -shape extends, while a large space is left for the resilient structure on opposite sides of the hook member 16.

In Fig. 9, one of the hydraulic cylinders 13 is schematically shown in more detail, in combination with a shaft 59 via which the hydraulic cylinder 13 is hinged to a beam 21 and a further support 58 of the frame 9. The shaft 59 is fixed relative to the frame 9 and pressure supply conduits 60, 61 are connected to bores 62, 63 extending through the axle 59. The bores 62, 63 communicate via ports 64, 65 with circumferentially extending grooves 66, 67 in the outer surface of the shaft 59. The grooves 66, 67 communicate with conduits 68, 69 extending through a piston rod 70 in longitudinal direction of the piston rod 70. The piston rod 70 interconnects a bush 71 around the shaft

59 with a piston 72. The piston 72 divides a chamber inside a cylinder housing 75 in an extension chamber 73 and a retraction chamber 74. The cylinder housing 75 is connected to the hook-lift arm 10 via a bush 76. The retraction chamber 74 communicates with a first one of the conduits 68 in the rod 70 and the extension chamber 73 communicates with a second one of the conduits 69 in the rod 70. Bearing material 77, 78 is arranged between the axle and the bush and sealings 79-81 extend circumferentially around the shaft 59 on both sides of each of the grooves 66, 67.

When pressure is applied to the pressure supply conduit 60 and hydraulic fluid is allowed to escape via the other pressure supply conduit 61, the pressure is transferred via the bore 62, the port 64, the groove 66 and the first conduit 68 to the chamber at the same side of the piston 72 as where the piston rod 70 is located. This causes the piston 72 to be displaced relative to the housing in a direction in which the piston rod 70 moving together with the piston 72 is retracted into the housing 75. The opposite effect is achieved when the second one of the pressure supply conduits 61 is pressurized and hydraulic fluid is allowed to escape via the first pressure supply conduit 60.

By providing the pressure supply conduits 60, 61 communicates with a pivotably. suspended hydraulic operating member 13 via a bearing between a fixed suspension member 59 and a pivotable suspension member 71 pivotably journalled relative to the fixed suspension member 59, the need of flexible conduits on the outside of the hydraulic operating members is avoided. Such flexible conduits can easily become damaged under harsh operating conditions. For this effect, the proximal part 11 does not need to comprise at least one extruded aluminium section 17, 18 extending in longitudinal direction of the proximal part 11, but in conjunction with such a feature conduits of the hydraulic system integrated in the sections can be coupled to the hydraulic operating members without conduits arranged outside the sections and the pivotable suspension of the hydraulic operating member.

That the at least one pressure supply conduit 60, 61) is connected to a shaft 59 that is fixed relative to the frame 9 and that has at least one circumferential groove 65, 66 communicating with a chamber 72, 73 of the hydraulic operating member 13. is advantageous, because the pressure supply conduits connect to a part that does not move relative to the frame and the supply conduits, when in operation.