1. Field of the Invention
The invention relates to a method for changing one or several dimensions of a load space in a working machine. The invention also relates to a method for changing the height of a load space in a working machine. Furthermore, the invention relates to an apparatus for changing one or several dimensions of a load space in a working machine.
2. Description of the Related Art
For harvesting, working machines, such as harvesters are known which move on a terrain by means of wheels or tracks and in which a harvesting device, a so-called harvester head, is provided at the end of a boom assembly for cutting, felling, and delimbing a standing tree stem and sawing it to pieces of desired length. The sawn tree stems are collected with a forwarder equipped with a grapple, and transported in its load space. A known load-carrying vehicle, movable by means of wheels is disclosed in the application publication WO 91/14610, said working machine comprising two frame parts connected to each other by means of a joint. The rear frame is equipped with a load space in which the tree stems are collected. The front frame is equipped with a cabin and a power source for the working machine.
For changing the load space of a forwarder, there is a known apparatus according to the publication SE 420699, in which the stakes restricting the load space can be extended telescopically. Publication SE 426677A also discloses a telescopically operating apparatus, wherein the height of the stakes and their mutual distance can be adjusted. The systems are intended especially for compression of the load. There is a known solution according to the patent publication FI 76295 for changing the length of the load space.
It is necessary to change the surface area and height of the load space so that the entire capacity of the load-carrying vehicle could be utilized, especially in the case of wood material and/or tree stems that is/are lighter or shorter than usual. Thus, the maximum capacity and maximum loadbearing capacity are not utilized even if the load space is full, wherein it is possible to increase the quantity of timber from normal by expanding the load space. Some solutions of related art have the drawback that it is often impossible and even dangerous to open manual lockings, especially when the load space contains timber. Thus, the load space must be adjusted beforehand, but it is difficult to predict the quantity and weight of timber beforehand.
The size of the load space can also be changed by means of pressurized medium operated actuators, which is safe, because it is possible to control the actuators from the cabin of the working machine. The systems require for example a control circuit, pipes and cylinders that are installed and integrated in the stakes. Thus, it is easy to adjust the load space in its maximum and minimum position, but it is still difficult to estimate the weight and quantity.
There are known weighing devices for weighing a load to be lifted up by a grapple, such as single tree stem or a bundle of stems, said weighing devices being coupled between the end of the boom assembly and the grapple. The device collects information on the quantity loaded in the load space. There are also known weighing devices installed in the bunks of the load space, and on the basis of the loading of said weighing devices it is possible to measure the weight of the loaded timber. By means of the measurement it is now also possible to monitor that the maximum capacity of the forwarder is not exceeded. There are also other known weighing devices that can be based for example on the identification of the loading exerted on the wheels or affecting in the structures, on the basis of which the increased load can be determined.
The load spaces that identify only the maximum and minimum position and/or that are based solely on the act of monitoring whether the maximum capacity is exceeded during the loading, are inadequate. The width of the load space and the location of the centre of gravity have an effect especially thereon in which kind of terrain and in how narrow surroundings in a forest it is possible to move for example with a forwarder. This is not taken into account in present systems in any way, wherein optimization of the various relevant factors is not possible. A load space that is positioned in a stepwise or continuous manner makes it possible to conduct even small changes, but if the driver is inexperienced, unnecessary changes and interruptions may occur during the work. As a result, the user may be distracted from the actual loading work, and making decisions relating to the changes takes time and requires actions to be taken.