Pallet trucks, especially low-lift pallet trucks

Abstract

Pallet truck (1), in particular low-lift pallet truck, with a drive unit (2) and a load unit (3) that is vertically movable relative to the drive unit (2) by means of a lifting device (15), wherein the lifting device (15) is designed as an electrically operated threaded spindle drive (16), in particular a ball screw drive, wherein the threaded spindle drive (16) has a threaded spindle (17) operatively connected to the drive unit (2) and a spindle nut (18) that is operatively connected to the load unit (3), characterized in that the threaded spindle drive (16) is arranged within a cover (33) of the pallet truck (1), which is provided with a recess (34) above the threaded spindle (17), wherein the threaded spindle (17) is accessible from above via the recess (34) in the cover (33), so that the threaded spindle (17) can be manually adjusted via the recess (34) with a key or a crank. is operable.

Description

[0001] The invention relates to a pallet truck, in particular a low-lift pallet truck, with a drive part and a load part that can be moved vertically relative to the drive part by means of a lifting device, wherein the lifting device is designed as an electrically operated threaded spindle drive, in particular a ball screw drive, wherein the threaded spindle drive has a threaded spindle in operative connection with the drive part and a spindle nut that is in operative connection with the load part.

[0002] In pallet trucks designed as low-lift pallet trucks, it is known to provide a hydraulic lifting device for raising and lowering the load relative to the drive unit. This device consists of a lifting cylinder located between the drive unit and the load unit. In manually operated low-lift pallet trucks, a hydraulic pump, operated by a tiller, supplies the lifting cylinder and thus lifts the load. In low-lift pallet trucks with a battery-electric drive system, an electric pump unit with a hydraulic pump driven by an electric motor is provided to supply the lifting cylinder with hydraulic fluid. The lifting and lowering movement is controlled by a suitable valve assembly, which is connected to the hydraulic cylinder, the hydraulic pump, and a hydraulic fluid reservoir via appropriate hydraulic fluid lines. However, such a hydraulic lifting device is complex to construct.Furthermore, a hydraulic lifting device requires constant maintenance, such as checking the hydraulic fluid level and regularly changing the hydraulic fluid and the corresponding filter. Additionally, excessive use of the lifting truck can damage the sealing components of the hydraulic lifting device, particularly in the area of ​​the lifting cylinder, leading to hydraulic fluid leakage into the surrounding environment.

[0003] From DE 698 19 353 T2, a lifting truck of this type is known, comprising a drive section formed by a frame element and a load section that is vertically movable relative to the drive section by means of a lifting device and is formed by a lifting plate arranged on a support element. An electrically operated threaded spindle drive is provided for raising and lowering the lifting plate, comprising a screw element driven by an electric drive motor as the threaded spindle. The screw element is arranged in a lifting mast-like lifting post of the frame element. A threaded ring element is arranged on the screw element as a spindle nut, which is arranged on a runner connected to the support element.

[0004] The present invention is based on the objective of providing a pallet truck of the type mentioned at the outset, whose lifting device has a low construction effort and enables improved operation of the pallet truck.

[0005] This problem is solved according to the invention by arranging the threaded spindle drive within a cover of the lifting platform, which is provided with a recess above the threaded spindle. The threaded spindle is accessible from above via the recess in the cover, allowing it to be manually operated with a key or crank. An electric threaded spindle drive, whose threaded spindle is attached to the drive unit and whose linearly movable spindle nut is connected to the load unit, can easily generate a linear movement for raising or lowering the load unit relative to the drive unit. Compared to a hydraulic lifting device consisting of a lifting cylinder, a hydraulic pump, a valve assembly, and a pressure reservoir, an electric threaded spindle drive offers reduced design complexity and lower manufacturing costs.Furthermore, such a lifting device, formed by an electric lead screw drive, in particular a ball screw drive, operates maintenance-free and exhibits robust operating characteristics, while also preventing leakage of hydraulic fluid to the environment due to the absence of hydraulic fluid. A ball screw drive also enables high lifting and lowering speeds with high precision.

[0006] According to the invention, the threaded spindle drive is arranged within a cover of the pallet truck, the cover being provided with a recess above the threaded spindle. The threaded spindle is accessible from above via this recess in the cover, allowing the threaded spindle to be mechanically actuated via the recess using a suitable key or crank in the event of a drive motor failure or a discharged battery of the pallet truck. This enables the continued operation of the pallet truck and, in particular, the lowering of the load section and thus the load itself.

[0007] According to a preferred embodiment, the threaded spindle is connected to an electric drive motor, in particular a permanent magnet motor, via a reduction gear. With a permanent magnet electric motor, the threaded spindle can be driven with minimal construction effort and space requirements, thanks to the use of a reduction gear.

[0008] The reduction gear can be designed as a gear drive, for example, a single-stage or multi-stage spur gear drive. It is also possible to design the reduction gear as a belt drive, for example, with a V-belt or toothed belt. Furthermore, overload protection can be easily implemented with a belt drive.

[0009] Advantageously, the threaded spindle drive is equipped with a braking device. With a braking device, for example a mechanical braking device arranged on the threaded spindle, in particular a spring-applied brake, a load arranged on the load-bearing component can be easily held in the raised position when the electric motor is not activated.

[0010] With regard to a simple design, particular advantages arise if, according to one embodiment of the invention, the spindle nut is provided with at least one fastening pin for connection to the load-bearing element. For example, with two fastening pins arranged laterally and opposite each other on the spindle nut, the load-bearing element can be easily connected to and fastened to the spindle nut.

[0011] According to an advantageous embodiment of the invention, the spindle nut is arranged in a tubular housing, the housing being provided with an elongated recess for guiding the mounting pin. Such vertically arranged elongated recesses, each guiding a mounting pin, allow for simple anti-rotation of the spindle nut and thus linear guidance.

[0012] The load part of the pallet truck expediently has a vertical bracket section which is provided with a mounting flange for the mounting pin, allowing the load part to be attached to the two mounting pins of the spindle nut with minimal construction effort.

[0013] With regard to a favorable installation space requirement in the longitudinal direction of the pallet truck, particular advantages arise if, according to a suitable further development of the invention, the threaded spindle drive is arranged in the longitudinal direction of the pallet truck, wherein the drive motor is arranged between the threaded spindle and the load part.

[0014] In this type of threaded spindle drive arrangement, the mounting flange is formed by a vertical mounting plate, in particular a U-shaped mounting plate, which surrounds the drive motor longitudinally along the pallet truck and thus laterally. With such a U-shaped mounting plate, the load component can be attached to the two lateral mounting pins of the spindle nut with minimal construction effort and in a robust design.

[0015] The construction effort in the manufacture of the pallet truck can be further reduced if the threaded spindle drive is designed as a pre-assembled module that can be attached to the drive unit.

[0016] According to a preferred embodiment, the drive unit has a U-shaped frame section which is provided with a mounting plate for the threaded spindle drive. Such a drive unit with a U-shaped frame section enables a stable design of the drive unit with minimal construction effort and allows for simple and quick attachment of the threaded spindle drive, which is designed as a pre-assembled unit, via the mounting plate.

[0017] If a pin for the steerable attachment of a drive-side wheel is arranged on the mounting plate, simple attachment of the steerable wheel to the drive part is still possible.

[0018] Advantageously, the recess can be closed by means of a cover cap, in particular a display device. The recess in the cover for emergency operation of the threaded spindle can be easily closed by means of a cover cap. Preferably, the cover cap is formed by a display device, for example a display, on which operating states and operating parameters of the pallet truck are shown.

[0019] Further advantages and details of the invention are explained in more detail with reference to the exemplary embodiments shown in the schematic figures. These show Fig. 1 a pallet truck according to the invention in a perspective view, Fig. 2 the drive part of the pallet truck Fig. 1 in a perspective view, Fig. 3 the threaded spindle drive in an enlarged view and Fig. 4 the bow-shaped frame section of the drive unit in an enlarged view.

[0020] In the Fig. Figure 1 shows a low-lift pallet truck 1 according to the invention, designed as a tiller-guided pallet truck, with a drive unit 2 and a load unit 3 that is vertically movable relative to the drive unit 2. The drive unit 2 comprises a U-shaped frame section 4, within which a wheel 5 is arranged to be steerable about a vertical pivot axis. The pallet truck 1 is steered by means of a tiller 6 connected to the wheel 5 and arranged to pivot about a horizontal pivot axis. The wheel 5 is designed as a pneumatic tire.

[0021] The load section 3 comprises two load arms 7a, 7b, with the load section 3 being supported on a track by means of load rollers 11a, 11b arranged at the ends of the load arms 7a, 7b. Loads, such as pallets, wire mesh boxes, or small parts containers, can be picked up, lifted, and transported using the load arms 7a, 7b. A vertical bracket section 8 is arranged on the load section 3 in the area facing the drive section 2. A battery compartment for a battery 9 can be attached to this bracket, which supplies electrical energy to the electric drive system of the pallet truck 1.

[0022] The load part 3 is arranged to be movable in the vertical direction on the bow-shaped frame section 4 of the drive part 2 by means of a lever arrangement formed by articulated levers 10.

[0023] The load rollers 11a, 11b arranged on the load arms 7a, 7b are rotatably mounted in load roller carriers (not shown) which are pivotally mounted on the load arms 7a, 7b. The load roller carriers are each secured by means of a Fig. The linkage 12 shown in Figure 2 is operatively connected to the corresponding articulated lever 10, whereby a lifting movement of the load part 3 relative to the drive part 2 is converted into a vertical movement of the load rollers 11a, 11b by means of the articulated levers 10 and the linkage 12, thus enabling the load part 3 to be raised and lowered relative to the drive part 2. The linkages 12 can be designed as push rods or pull rods arranged within the load arms 7a, 7b.

[0024] The U-shaped frame section 4 of the drive unit 2 and the load unit 3 formed by the load arms 7a, 7b and the vertical frame section 9 are, in the pallet truck 1 according to the invention, formed from one-piece hollow profiles, for example tubular profiles, with a closed cross-section, which gives the pallet truck 1 a low dead weight while providing high stability and strength. This design of the drive unit 2 and the load unit 3, in conjunction with the pneumatic tire 5, makes the pallet truck 1 according to the invention particularly suitable for applications outside of warehouses and production facilities with uneven surfaces, for example on roads and squares.

[0025] The pallet truck 1 according to the invention can be equipped with a battery-electric drive system for driving the wheel 5, in particular by means of an electric drive motor designed as a wheel hub motor, which is supplied with electrical energy by the battery 9.

[0026] Alternatively, the pallet truck 1 according to the invention can be manually operated. In such a pallet truck, the wheel 5 is not driven by an electric drive motor.

[0027] To raise or lower the load part 3 relative to the drive part 2, a lifting device 15 is arranged between the load part 3 and the drive part 2, which according to the invention is designed as an electric threaded spindle drive 16.

[0028] The threaded spindle drive 16 comprises - as in the Fig. Figure 3 shows a vertically arranged threaded spindle 17 and a spindle nut 18 arranged to be longitudinally displaceable on the threaded spindle 17. An electric drive motor 19 is provided to drive the threaded spindle 17. This motor is connected to the threaded spindle 17 via a multi-stage reduction gear 20 designed as a gear unit. The drive motor 19 is supplied with electrical energy by the battery 9.

[0029] The threaded spindle drive 16 is equipped with a braking device 21 which is operatively connected to the threaded spindle 17.

[0030] The threaded spindle drive 16 is designed as a pre-assembled unit and comprises a flange plate 22, on the upper side of which the drive motor 19 and the threaded spindle 17 are arranged and attached, and on the underside of which the reduction gear 20 is arranged and attached within a corresponding housing. The threaded spindle 17 is arranged within a tubular housing 27 attached to the flange plate 22.

[0031] To attach the threaded spindle drive 16 to the drive part 2, the U-shaped frame section 4 of the drive part 2 is used - as shown in the Fig. Figure 4 shows a horizontal mounting plate 23 to which the flange plate 22 can be screwed using appropriate mounting screws. A recess 24 for receiving the reduction gear 20 is formed in the mounting plate 23 in order to minimize the overall height of the drive unit 2 when the threaded spindle drive 16 is mounted. A mounting pin 25 is also arranged on the underside of the mounting plate 23, to which a bearing fork 26 for receiving the steerable wheel can be attached – as shown in the figure 4. Fig. 2 shown - can be rotatably mounted about the vertical pivot axis. The drawbar 6, which pivots about the horizontal pivot axis, is also arranged on the bearing fork 26.

[0032] As in the Fig. As shown in Figure 2, the threaded spindle drive 16 is arranged in the longitudinal direction of the lifting trolley 1, with the threaded spindle 17 facing the drawbar 6 and the drive motor 19 facing the load part 3.

[0033] The spindle nut 18 is provided with two mounting pins 30, arranged laterally and thus opposite each other in the transverse direction of the vehicle, for connection to the load part 3. The vertical bracket section 8 of the load part 3 is provided with a mounting flange 31 in its central upper area for connection to the mounting pins 30. The mounting flange 31 is formed by a vertically arranged, U-shaped mounting plate 32, which laterally surrounds the drive motor 19 on both sides in the longitudinal direction of the vehicle. The mounting plate 32 can be provided with bore-shaped receptacles by means of which the mounting plate 32 can be attached to the mounting pins 30.To prevent the spindle nut 18 from rotating, the tubular housing 27 which receives the threaded spindle 17 is provided for each mounting pin 30 with a vertically arranged, elongated recess 28 in which the corresponding mounting pin 30 is arranged and guided.

[0034] The lifting device 15 formed by the threaded spindle drive 16 is mounted on the lifting trolley 1 within a space in the Fig.The threaded spindle 17 is arranged in the cover 33 shown in Figure 1. Above the threaded spindle 17, the cover 33 has a recess 34 which can be closed by means of a cover cap 35 formed by a display device. With the cover cap 35 removed, the threaded spindle 17 is thus accessible from above via the recess 34 in the cover 33 and can be manually operated by means of a suitable key or crank to enable manual operation of the pallet truck 1 and to lower the load part 3 when the battery 9 is discharged.

[0035] The lifting device formed by the electric lead screw drive 16 according to the invention has a number of advantages. Compared to a hydraulic lifting device with a hydraulic pump, the lead screw drive according to the invention produces less operating noise. Furthermore, the absence of a hydraulic fluid eliminates the risk of leakage into the environment when the pallet truck 1 tips over or due to damaged seals on a hydraulic lifting device. In addition, maintenance-free operation of the electric lead screw drive 16 is achievable, even when the pallet truck 1 is operated on streets and squares and under high loads, for example, when driving over larger obstacles, especially driveways and curbs or curb ramps.

[0036] By designing the threaded spindle drive 16 as a pre-assembled module, simple manufacturing and assembly on the bow-shaped frame section 4 of the drive part 2 can be achieved, and in conjunction with the drive part 2 and load part 3, which consist of tubular profiles, a low dead weight of the pallet truck 1 can be achieved, which facilitates operation on streets and squares.

Claims

[1] Lifting truck (1), in particular a low-lift truck, with a drive part (2) and a load part (3) which is vertically movable relative to the drive part (2) by means of a lifting device (15), wherein the lifting device (15) is designed as an electrically operated threaded spindle drive (16), in particular a ball screw drive, wherein the threaded spindle drive (16) has a threaded spindle (17) which is operatively connected to the drive part (2) and a spindle nut (18) which is operatively connected to the load part (3), characterized by that the threaded spindle drive (16) is arranged within a cover (33) of the lifting carriage (1), which is provided with a recess (34) above the threaded spindle (17), wherein the threaded spindle (17) is accessible from above via the recess (34) in the cover (33), so that the threaded spindle (17) can be manually actuated via the recess (34) with a key or a crank. [2] Lifting truck according to claim 1, characterized bythat the threaded spindle (17) is in driving connection with an electric drive motor (19), in particular a permanent magnet motor, via the interposition of a reduction gear (20). [3] Lifting truck according to claim 2, characterized by that the reduction gear (20) is designed as a gear transmission. [4] Lifting truck according to claim 2, characterized by that the reduction gear (20) is designed as a belt drive. [5] Lifting truck according to one of claims 1 to 4, characterized by that the threaded spindle drive (16) is provided with a braking device (21). [6] Lifting truck according to one of claims 1 to 5, characterized by that the spindle nut (18) is provided with at least one fastening pin (30) for connection to the load part (3). [7] Lift truck according to claim 6, characterized bythat the spindle nut (18) is arranged in a tubular housing (27), wherein the housing (27) is provided with a slot-like recess (28) for guiding the fastening pin (30). [8] Lifting truck according to claim 6 or 7, characterized by that the load part (3) has a vertical bracket section (8) which is provided with a fastening flange (31) for the fastening pin (30). [9] Lifting truck according to one of claims 2 to 8, characterized by that the threaded spindle drive (16) is arranged in the longitudinal direction of the lifting carriage (1), wherein the drive motor (19) is arranged between the threaded spindle (17) and the load part (3). [10] Lifting truck according to claim 8 or 9, characterized by that the fastening flange (31) is formed by a vertical holding plate (32), in particular a U-shaped holding plate, which surrounds the drive motor (19) in the longitudinal direction of the lifting carriage (1). [11] Lifting truck according to one of claims 1 to 10, characterized by that the threaded spindle drive (16) is designed as a pre-assembly unit which can be fastened to the drive part (2). [12] Lifting truck according to one of claims 1 to 11, characterized by that the drive part (2) has a bow-shaped frame section (4) which is provided with a fastening plate (23) for the threaded spindle drive (16). [13] Lift truck according to claim 12, characterized by that a pin (25) for the steerable fastening of a drive part-side wheel (5) is arranged on the fastening plate (23). [14] Lifting truck according to one of claims 1 to 13, characterized by that the recess (34) can be closed by means of a cover cap (35), in particular a display device.

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