EP1110904B1

EP1110904B1 - Fork truck with a device for lateral movement of load taking means

Info

Publication number: EP1110904B1
Application number: EP20000850208
Authority: EP
Inventors: Magnus Alveteg
Original assignee: BT Industries AB
Current assignee: BT Industries AB
Priority date: 1999-12-16
Filing date: 2000-12-12
Publication date: 2006-02-01
Anticipated expiration: 2020-12-12
Also published as: DE60025802D1; SE9904607L; SE521939C2; DE60025802T2; SE9904607D0; EP1110904A1

Description

This invention is in particularly related to the type of load taking trucks that can pivot or turn load taking means to the left and right, as for instance load forks or these supporting means, for instance a beam or mast, so called "swing reach trucks". These trucks operate in such a manner that they without turning themselves move forth and back in the aisles between the pallet shelfs. Since the forks are pivotable from left to right and moveable laterally or transversely in relation to the truck the forks put down and pick up pallets in shelfs on both sides of an aisle without the truck having to turn and the aisles between the pallet shelfs may therefor be narrow. Frequently these trucks are also designed in such a manner that the driver in a drivers cage accompany the forks in the movement up and down, for instance for the use of the truck also as a picking truck, that is the operator (driver) picks merchandise by hand from the shelfs and put these directly on a pallet or into a container on a pallet that rests on the forks. These trucks are therefor often called combi trucks. Mostly the load forks are also moveable heightwise in relation to the drivers or operators cage so that the load forks of the truck can reach higher than the operators cage among other things in order to achieve an ergonomic height of working. At a known truck of this type the movement laterally of the forks, that is in and out of the pallet shelfs is achieved by the entire fork mast being displaced laterally in relation to the drivers cage. Guides for the movement are arranged on fork mast and drivers cage respectively and in order to achieve the lateral movement two horizontal transverse racks are arranged on the front wall of the drivers cage. Two pinions connected with an axle joumaled in the fork mast mesh with the racks and are rotated by the motor when lateral movement is to take place. By the arrangement of a joint driving in the upper end as well as in the lower end the risk of chest drawer effects is reduced as the need of guides.
A draw back with the rack and pinion drives is the risk of the drivers or others getting caught. Further continuous greasing and service is required. The grease with which the racks as well as the pinions have to be greased collect dust and the grease may form lumps or drops that may fall down and contaminate not only the floor but also the goods, for instance in the shape of food, and the racks are thus a pollution source. Even if a good maintenance can keep this to a minimum the need of service will be large. Further can be noted that racks are a comparatively expensive solution that may result in disturbing vibrations.
Other ways of propelling movements are known also from the truck field, for instance is in DE 32 29 868 described the use of two flexible strings that circulate in different ways.
In another document, DE 196 24 874, movement is obtained with chains.
The object of the invention is to mitigate the above problems and drawbacks respectively. In accordance with the invention this is achieved with a driving by means of cogbelts. One or two cogbelts may be used that extend horizontally over the entire width of the drivers cage, cabin or width of the truck. The belt has its cogs facing the cage and extend at the fork mast over two pulleys out in a loop around a cogwheel. By rotation of the cogwheel the toothed belt is drawn in on one side and the forks are moved laterally together with the fork mast. In order to secure a parallel movement it is possible to arrange a cogbelt in the upper end of the truck and one in the lower end parallel to each other and with connected cogwheels.
The driving of the cogwheels may preferably be achieved by arranging a drive for the connecting axle, for instance in the shape of a hydraulic motor and a driving belt.
By the use of the above described driving means a considerably neater and cleaner installation is obtained that needs less service. Furthermore the guides for the movement require far less space than in the known solution with racks. An additional advantage is that the driving means become essentially more silent and free from vibrations, which essentially contributes to an improved environment, in particular for the driver.
Additional advantages and characteristics of the invention are apparent from the sub claims as well as from the following description of a preferred embodiment in accordance with the invention with reference to the drawings. At this Fig 1 shows a truck equipped in accordance with the invention in a lateral view, Fig 2 the fork mast and the drivers cage in a larger scale and Fig 3 the drive itself schematically shown from above.
The truck shown in fig 1 includes a mid steered lower part with motor and battery in the rear part 2 and a telescopically extendable mast 1 in the front part 3. On the outer telescopic part of the mast a vertically moveable drivers cage 4 with a platform 5 and a roof 6 is arranged for the driver. In front of the driver a load taking means in the form of a pair 7 of load forks are arranged on a fork carriage 24 that is moveable in a vertical direction in a vertical guiding on a fork mast 25. The fork mast is in turn pivotable 180° in a fork mast holder 26. The pivoting takes place with two hydraulic cylinders 31 the piston rods of which are connected with a roller chain which grips into a sprocket connected to the mast. In this way the fork mast and with this the forks can be turned to the left, to the right or straight forward as desired.
The fork mast holder 26 includes in addition to journals for the fork mast a vertical beam 27 connecting the journals with each other and extending from the floor of the drivers cage to its roof. In the lower end of the fork mast holder 26 a roller 28 is arranged in order to make it possible for the mast holder 26 to move laterally, which roller transfers the vertical loads from the holder to the drivers cage, which roller runs in a U-beam 29 enclosing the roller and being fastened to the bottom of the drivers cage. For the journaling and guiding of the fork mast holder 26 lengthwise of the truck additionally upper 29 and lower 13 U-beams are arranged at the platform 5 of the drivers cage and the roof 6 of this respectively with the rollers running therein fastened to the fork mast holder 26.
The lateral movement of the fork mast 25 and thereby the forks 7 is achieved with two drives arranged in the upper end and the lower end of the drivers cage. The driving means are built in the way that is shown in Fig 3. The device shown in Fig 3 includes a sturdy cogbelt 10 that extends along a horizontal beam 11 in the roof of the drivers cage, which beam 11 in its ends is provided with rollers 12 around which the cogbelt extends then to be fastened in both ends to the beam 11 and thereby to the drivers cage by clamping means 13 that grip into the profile of the cogbelt. The ends of the cogbelt are fastened to the beam via pullrods that are threaded and the cogbelt can in this way be pretensioned.
The cogbelt 10 is further in what we could call an omega drive (after the greek letter Ω) bent out of from the straight path between the rollers 12 in the ends of the beam 11 over pulleys 19 and further around a driving cogwheel 20 that in a not shown way is journaled in the vertical beam 27 of the fork mast holder. The cogs of the cog belt face the beam 11 and the cogwheel in the fork mast holder respectively.
The turning of the driving cogwheel 20 means that the mast is moved along the belt and thereby transversely in relation to the drivers cage.
The driving cog wheel 20 is fastened to an axle 8 that connects the two essentially identical driving devices at the roof and bottom of the drivers cage. Further an additional cogwheel 21 is arranged on the axle and is by means of a drive belt 22 connected to a hydraulic motor 23 that delivers the required power when the fork mast is to be moved laterally in relation to the drivers cage.
When the lateral driving is activated in one direction, for instance to the right in fig 3 a pulling force is established in the right part of the cogbelt 10 and result in shortening of this part of the belt. In the opposite end of the belt the pretensioning force is reduced corresponding to the driving force and if this is greater than the pretension force the belt would slacken. In order to prevent this a spring 14 is arranged at each pullrod and when the pretension is reduced below certain value a stop 18 for the pullrod lifts from a tube shaped bracket 16 on the beam 11. By means of the springs the otherwise required pretensions force (to prevent slacking) of the cog belt can be reduced, which in turn means that the cogbelt may be dimensioned more narrow than otherwise would have been the case. When the driving movement stops the pretension of the cog belt once again pulls the pull rod against its rigid stop with its stop 18 in contact with the tube bracket 16 while compressing the spring 14.
Since the belt all the time is stretched the risk for play and strikes in the driving movement forth and back is eliminated which further increases the precision in the work at the same time as the risk of shocks and noises is reduced. Likewise the wear of the teeth or cogs of the cogbelt that otherwise may arise at slackening cogbelt due to improper meshing between cogbelt and cog wheel is reduced. The adjustment possibilities of the cog belts in both ends may be used to adjust the upper and lower cogbelts between themselves so that the fork mast is held entirely vertical. At mounting one can consider that the nuts of the pull rods are first tightened so that the stops come to contact against the tube shaped guiding boxes, whereafter additionally a number of (calculated) turns can be taken in order to achieve the intended pretension.
Since the cogwheels 20 can be located arbitrarily far from the drivers cage the driving axle 8 and the vertical beam 20 may be placed outside of the movement area that is desired as available for the driver. One can even by arranging the fork guiding on the fork mast only on the side of the fork mast facing the forks enable an arranging of the common drive axle in the mast itself so that the vertical beam may be eliminated with additionally improved sight and freedom of movement for the driver as result.
If so is desired the cogbelt may be fastened in the pulleys in the ends of the beam, at which the pulleys may be provided with stops as well as pretensioning means for instance in the shape of torsion springs.

Claims

Fork truck that can pivot or turn load taking means to the left and the right, as for instance load forks or their supporting means and with a device for lateral movement of the load taking means, for instance a beam or a mast (25), characterized in that the device includes a cogbelt (10), that extends horizontally over the entire width of the truck and that the cogbelt (10) has its cogs facing the truck or preferably a drivers cage (4) on this, and at the load taking means (25) the cogbelt via two pulleys (19) runs out in a loop around a cogwheel (20) joumaled in the load taking means, so that by rotation of the cogwheel the cogbelt is drawn in around the cog wheel and out on the other side moving the load taking means (25) laterally.
Truck according to claim 1, characterized in that one belt drive is arranged in the upper end of the load taking means (25) and one additional in the lower end of the load taking means and that driving cog wheels (20) and an axle (8) connecting these are arranged in the load taking means or a beam parallel with this means.
Truck according to claim 2, characterized in that the upper driving means is arranged at the roof of the drivers cage and the lower at the floor of the drivers cage.
Truck according to the any of the preceding claims, characterized in that the cogbelt is pretensioned against substantially rigid stops (18, 16) in both ends, which are unyielding to pulling but that springs (14) furthermore are arranged pulling in the extending direction of the cogbelt (10) from the stops so that the cogbelt is prevented from slackening even if the driving force exceeds the pretension.
Truck according to any of the claims 2 - 5, characterized in that the cogbelt or the cogbelts run over further pulleys (12) at the lateral edges of the truck enabling use of the entire extent of the cog belt laterally in relation to the truck for movement.
Truck in accordance with any of the preceding claims, characterized in that the pulleys (19) around which the cogbelt is bent out are arranged close to each other.
Truck in accordance with any of the preceding claims, characterized in that the cogbelt is fastened to the further pulleys (12), the further pulleys being provided with stops as well as pretensioning means.