Patent Application
20140231176
The present invention relates to the multitude of machines utilized to lift up loads, goods such as, without limitations, lifters or, for example, fork-lift trucks.
The forklift is a basic tool of today's industry, but not only: warehouses, distribution centres, manufacturing plants, factories, and many other commercial and agricultural applications depend on forklifts utilization to keep the daily work running easily. Forklifts are named for the L-shaped “forks” typically used to handle and to lift pallets, but the trucks can be outfitted with different accessories for picking up spools, drums, or other specific loads as well. These trucks, also called “lift trucks”, are available for both indoor and outdoor applications.
A lift truck is typically designed and includes the components as follows. The whole truck is a motive machine with wheels powered through a transmission and drive train. An engine is provided, for example a diesel or a gas powered internal combustion engine, or a battery-powered electric motor. A counter balance is attached to the rear of the machine, which is a heavy iron mass, necessary to compensate for the load handled. In an electric forklift the battery may serve also as a counterweight. Most important, the lift-truck includes a mast, which is the vertical assembly responsible for raising or lowering a load. A fork lift mast is made up of interlocking rails necessary to provide lateral stability. These rails or guideway structures are guided by rollers or bushings.
Depending on the application, typically some configurations are possible:
The mast is hydraulically operated and consists of cylinders and interlocking rails for lifting and lowering operations. Further, forks are provided, which are the L-shaped members that engage the load. The rear vertical portions of the forks are attached to a carriage and the front horizontal portions are inserted into or under the load, usually a pallet. Finally, a cabin with a seat for the operator is provided with pedals and switches for controlling the whole machine functions.
Usually the lift of the loads is performed by means of a hydraulic actuator. A hydraulic electro-pump supplies pressurized fluid (oil) to an hydraulic circuit (pipes, valves, distributors, actuators) to compose a system which also lifts the load by means of hydraulic cylinder. However, the efficiency of such hydraulic system is low. According to the hydraulic solution an estimate of the efficiency is related to the efficiency of the following components:
The problem underlying the present invention in view of the prior art is to provide a more energetically efficient lifting system.
The above-mentioned problem is solved by the lifter according to claim 1. According to a first aspect of the invention, the lifter, according to claim 1, comprises (
This has the advantage that a lifting of a load can be performed in two different ways. The first is a motion of the transmission means or transmission means system to which the load carrier is connected. By moving the transmission means, for example by turning if around one or more driving pinions and one or more guiding pinions, the load can be lifted. (
Another lifting of the load can be performed by lifting the movable mast structure relative to the fixed mast structure. In particular, the lifter can be configured to couple the two lifting motions. For example the two lifting motions can be performed one after the other. This implementation with the transmission means being connected to the movable mast structure but not to the fixed mast structure is called, in the first stage movement, “free-lift”.
The lifter according to the invention does not involve any hydraulic system, and, hence, avoids the low efficiency typical of such hydraulic system.
According to a development of the lifter according to the invention, the lifter may comprise means for driving the at least one transmission means. This is one particularly convenient implementation for lifting the load by driving and, hence, moving the at least one transmission means. (
According to a further development, the lifter may be configured to lift the load in a first stage by moving the transmission means along the loop path while lifting the toad carrier connected to the at least one transmission means, and the lifter may be configured to lift the load in a second stage by lifting the movable mast structure. (
According to another development of the lifter, the movable mast structure may be stationary during the first stage, and the at least one transmission means may be stationary along the loop path during the second stage. According to this implementation, the lifting process is divided into two distinct movements. First, the load carrier is lifted by driving the transmission means and keeping the movable mast structure stationary, and second, when the lifting motion of the transmission means has reached a certain limit, the load carrier is lifted further by lifting the mobile mast structure relative to the fixed mast structure. (
According to a further development the movable mast structure comprises a retainer for stopping the relative motion between the load carrier and the movable mast structure at the end of the first stage. This is an easy implementation for separating the two lifting stages.
According to another development, the lifter may further comprise at least one driving pinion for driving the at least one transmission means, the driving pinion being attached to the fixed mast structure. According to this development, for example the shaft of the driving pinion may be supported by the fixed mast structure for exerting a force on the at least one transmission means. In particular in combination with one or more retainer rollers, this provides for an effective lifting mechanism. (
According to a further development, the lifter may further comprise one or more retainer rollers for providing an engaging connection between the at least one driving pinion and the at least one transmission means. By using one or more retainer rollers the interaction of the driving pinion with the at least one transmission means can be secured and this allows the power transmission.
The above-mentioned problem is also solved by the lifter according to claim 6. According to a second aspect, the invention provides a lifter, comprising: (
This implementation of a lifter according to the invention is particularly useful for heavy load applications as a powerful motor may be used for driving the movable mast. The transmission means moves in response to the movement of the movable mast structure.
According to a development the lifter may further comprise means for driving the movable mast structure. In this implementation, the movable mast is driven, and not the transmission means as in the first aspect of the invention. While lifting the movable mast structure, also the at least one transmission means that is movably connected thereto is moved, thereby lifting the load carrier. In particular, the at least one transmission means may be connected to the movable mast structure via at least one guiding pinion.
According to a further development, the lifter may be configured to lift the load by simultaneously moving the movable mast structure and the at least one transmission means.
According to another development the lifter, according to the first and second aspect, may further comprise at least one rack, in particular a toothed rack, rigidly connected to the movable mast structure and at least one rack pinion engaging the at least one rack and for driving the at least one rack. In particular for the second aspect this provides for an easy provision of an interaction of the movable mast structure with the means for driving it (
According to a further development the lifter may comprise at least one guiding pinion, wherein the at least one guiding pinion is attached to the movable mast structure and is configured to guide the at least one transmission means.
According to another development of the first aspect and its developments, the lifter may comprise an additional movable mast structure and an additional transmission means system for providing a connection between the additional movable mast structure and the fixed mast structure, in particular configured to thereby implement a third lifting stage. (
According to a further development the lifter further comprises an electric motor for providing power for lifting the load carrier during a lifting phase, in particular for driving the at least one rack pinion or for driving the at least one driving pinion, more particularly, wherein the at least one transmission means is driven by the electric motor via a shaft and the at least one driving pinion being connected to the shaft.
According to another development, the electric motor may be configured to generate electric power under specific working conditions: during lowering phase the electric motor works in re generative mode (as generator) and provides energy to charge the battery of the lifter, or wherein the electric motor is connected to an electro-brake. The control brakes the moving part assembly and, in case, the load, too.
According to a further development, the lifter may comprise an epicycloidal gearbox connected to the electric motor, wherein an external ring gear of the gearbox engages a rack rigidly connected to the fixed part of the lifting structure (
The invention also provides a lift-truck comprising a lifter according to the invention or one of its developments, in particular comprising a further electric motor or a combustion motor for driving one or more wheels of the lift-truck.
According to a third aspect, the invention provides a lifter having: (
Developments of the third aspect, for example the driving of the transmission means, may be implemented as described in connection with the first aspect of the invention and the respective developments.
Further features and advantages of the present invention will be described in the following with reference to the figures, which illustrate only examples of embodiments of the present invention. The illustrated and described features may be suitably combined with each other, in particular with the features of the inventive electric lifter and its developments.
According to the invention as described above, the at least one transmission means can be at least one positive drive belt or at least one cog belt or at least one chain or at least one rack. The following embodiments include at least one transmission means chain for the at least one transmission means, however, just as an example.
In the drawings the reference numbers denote the following:
The most simple embodiment of the invention is described in
The clamping system of the forks carriage 120 and the transmission means 110 will be accurately studied to allow the transition through the driving pinion 100 and the retaining roll or rolls 180.
In particular, the invention provides the following embodiments:
An important feature has to be underlined: during the lifting phase the electric motor provides energy to the mobile part of the lifting structure and to the load which is accumulated as potential energy Wp:
Wp=L×h+L1×h1,
where
During the lowering phase this energy is given back to the electric motor that, in this operating condition, works like a generator and regenerates energy back to the mains or, for example, to the battery.
According to the electric solution with an electric motor and a gearbox an estimate of the efficiency η of the following components can be given: Electric motor: 80%, Reduction gearbox: 95%. Therefore, the total efficiency is about η: 0.8×0.95=76%.
The electric motor M is usually connected to an electronic power converter that regulates the power to the motor during the lifting phase (driving) and regulates the power of the generator back to the mains or to the battery during the lowering phase (regenerating).
Having described the preferred embodiments, it will become apparent that various modifications can be made, without departing from the scope of the invention as defined in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 13 155 442.0 | Feb 2013 | EP | regional |
