Abstract:
A mobile machine, in particular an industrial truck ( 1 ), includes at least one pressurized tank ( 3 ), in particular to carry fuel that is in a gaseous state under normal conditions. At least one molding ( 10, 15, 19, 21 ) that is adapted to significant portions of the external contour of the tank ( 3 ) is provided, and which is made of a high density material.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to German Application No. 10 2005 042 938.6, filed Sep. 9, 2005, which application is herein incorporated by reference in its entirety.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to a mobile machine, in particular an industrial truck, with at least one pressurized tank for carrying fuel which is in a gaseous state under normal conditions.  
         [0004]     2. Technical Considerations  
         [0005]     Mobile machines are frequently operated with fuels that are gaseous under normal (ambient) conditions. In addition to hydrocarbon-based fuels, such as propane, butane and methane, increasing use is being made of hydrogen, which can be used to operate a fuel cell unit, for example. The mobile machine generally has one or more pressurized tanks for the storage of these fuels. To be able to store the largest possible quantity of fuel, the tanks are generally pressurized at relatively high pressures, conventionally more than 25 bar and typically on the order of magnitude of 200 bar, as high as 350 bar for hydrogen, and, in individual cases, as high as 700 bar.  
         [0006]     In mobile machine applications, an objective is generally to make the components as lightweight as possible so as to increase the cargo-carrying capacity of the vehicle. With fuel tanks of the known art, attempts have consequently been made to design the fuel tanks so that they are as lightweight and simultaneously as stable as possible, for which reason aluminum alloys or compound materials can be used. An additional objective of tanks of the known art is to achieve maximum filling pressures and, therefore, maximum filling quantities while using the minimum amount of material. As a result of which, the tanks are generally cylindrical or spherical in shape. However, tanks of this type utilize the available space inefficiently, especially if two or more such tanks are located next to each other because unused space remains between the tanks or between the tanks and a housing wall, which is generally flat and straight. Locating the tank(s) outside the chassis of the vehicle, which is frequently done on vehicles that are operated with liquefied natural gas, avoids this problem. However, this has the disadvantage that the tank(s) are exposed without protection to environmental factors, including but not limited to mechanical damage and solar radiation. Also, outboard installation restricts accessibility to the vehicle and/or the view of the vehicle operator.  
         [0007]     Mobile machines with the same basic design are frequently equipped with different propulsion concepts, for example electric propulsion with a lead battery or an internal combustion engine with liquid fuels, or an electric motor with a fuel cell unit and gas fuel, or an internal combustion engine with gas propellant. One factor, among others, that determines the weight of the vehicle is the weight of the energy storage system, for example, the lead battery or the fuel tank. In particular, vehicles with an electric propulsion system and a lead battery are relatively heavy, given the same operating time. In the case of mobile machines, this weight is frequently desirable because, on industrial trucks, for example, the traction is improved or the weight of the battery can be used to provide a counterweight to the load being carried. The heavier the battery, the heavier the load that can be counterweighted by the battery.  
         [0008]     On the other hand, vehicles whose energy supply comes from fuel cells that are supplied with a gaseous fuel, such as hydrogen, for example, have a significantly lower weight. As a result of which, the useful load-carrying capacity is reduced, which, in turn, reduces the productivity of the vehicle. The safety of the vehicle is likewise reduced because, with the same load, the stability is significantly less than on an equivalent vehicle equipped with a lead battery.  
         [0009]     An object of the invention is, therefore, to create a mobile machine, in particular an industrial truck, with at least one pressurized tank, in particular to carry fuel that is in a gaseous state under normal conditions, which has a high level of operational safety and reliability and a long period of operation, has a simple construction, makes optimal utilization of space, and makes possible particularly economical operation.  
       SUMMARY OF THE INVENTION  
       [0010]     The invention teaches that a molding is provided that is fitted to at least significant portions of the external contour of the tank, which molding is made of a high-density material. “High density”, as used here, means a density of greater than 6 kg/dm 3 , such as greater than 7 kg/dm 3 . The space surrounding the tank, which in conventional systems generally remains unused on account of the complex shape of the tank, is thereby filled with heavy material. In this manner, the traction of the vehicle and its stability are increased significantly. Because the spaces filled by air in vehicles of the known art are occupied by the molding, the safety of the vehicle is also improved in the event of leaks in the fuel system because there is less ambient air that could form an explosive or flammable mixture with the fuel.  
         [0011]     The molding is advantageously fitted to the contour of the components that surround the tank. The empty space between the tank and the surrounding components is thereby occupied as fully as possible.  
         [0012]     It is also advantageous if the molding is fitted to significant parts of the external contour of at least one additional tank. In known systems having two or more tanks, the amount of unused space is particularly large, especially when the tanks in question are cylindrical or spherical. By fitting the molding of the invention to the contour of the tank, the space between the tanks can be effectively filled.  
         [0013]     In one advantageous configuration of the invention, the molding has at least one recess with at least an approximately circular arc-shaped cross section to hold at least one tank. Tanks generally have cylindrical or spherical external contours, which can be enclosed particularly firmly in a recess of this type.  
         [0014]     It is advantageous if at least one elastic element is located in the recess that holds the tank. The tank is, therefore, not in direct contact with the molding and is vibrationally isolated from it. The wear and abrasion of the molding and the tank in the event of mutual, even minimal, movements is thereby significantly reduced or even totally eliminated.  
         [0015]     In one advantageous configuration of the invention, the molding can be made of metal, e.g., a ferrous material, in particular steel or cast iron. Ferrous materials are economical, easy to work, and have a relatively high density.  
         [0016]     In an additional advantageous configuration, the molding can be formed from a lead alloy. Lead has a high density, is relatively economical and easy to shape, and can be closely fitted to complex geometries.  
         [0017]     It is further appropriate if the molding has at least one approximately plane (flat) lateral surface. The three-dimensional components of the mobile machine and the housings of the mobile machine or of the components used in it generally also have plane surfaces, so that there is particularly good contact between the plane surfaces and the molding. The introduction of forces is thereby distributed over a large surface area, which eliminates harmful peak or spot loads on the molding and/or on the mobile machine and/or on its components.  
         [0018]     In an additional advantageous realization of the invention, the molding has at least two approximately parallel lateral surfaces. The molding can, therefore, be made to fit in the vehicle particularly efficiently because there are contact surfaces on two sides that are at a constant distance from each other.  
         [0019]     The molding advantageously has at least one fastening device to connect the molding with the industrial truck. The molding can thereby be fastened in the vehicle using simple means, and the molding can be used for the fastening of the tank, which is securely fixed in position on account of the matching contour of the molding. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     Additional advantages and details of the invention are explained in greater detail below on the basis of the exemplary embodiment illustrated in the accompanying drawings. Identical parts are identified by the same reference numbers throughout.  
         [0021]      FIG. 1  shows a counterweighted fork lift truck as one example of a mobile machine of the invention;  
         [0022]      FIG. 2  shows two pressurized tanks with three moldings of the invention, and a detail showing two moldings; and  
         [0023]      FIG. 3  shows a molding of the invention to hold four pressurized tanks. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]      FIG. 1  shows a counterweighted fork lift truck  1  with a fuel cell unit  2  and a pressurized hydrogen tank  3  as one example of a mobile machine of the invention. Loads are held and transported on load-holding means  4  (such as forks) that are not shown in any further detail in the drawings. To compensate for the weight of the load, there is a counterweight  5  in the stem area of the fork lift truck  1 . Between a front axle  6  and a rear axle  7  of the fork lift truck  1  there is a housing compartment  8  that would hold the battery if the fork lift truck were electrically operated and powered by a battery. In the fork lift truck  1  shown in the illustration, this housing compartment  8  contains the fuel cell unit  2 , the hydrogen tank  3 , and additional auxiliary units  9 . The hydrogen tank  3  has the basic cylindrical shape that is conventional for such applications in the known art and is advantageously lightweight for mobile applications, for example as a result of the use of an aluminum alloy or of a fiber-reinforced composite material and/or, when steel is used, use of a minimal wall thickness.  
         [0025]     The hydrogen tank  3  is surrounded by two, high-density moldings  10  of the invention, each of which has a recess  11  in the shape of a circular arc that fits the external contour of the tank  3 . The moldings  10 , therefore, have an essentially rectangular outer cross section, which is interrupted by the circular arc-shaped recess  11 . Sides  12  of the molding  10  that face away from the recess  11  are each flat so that the molding is in contact over a large surface area with a floor  13  and wall  14  of the housing compartment  8 . Above the tank  3 , too, there is a flat surface  12   a  available, on which, in the illustrated exemplary embodiment, the fuel cell unit  2  is located. The moldings  10  are fastened to the industrial truck  1  by threaded fasteners T, as a result of which the moldings  10  simultaneously act as a holding device for the tank  3 . The fuel cell unit  2  can also be fastened to the moldings  10 , so that no independent fastening device is necessary.  
         [0026]     The space in industrial trucks that is occupied by the moldings  10  is typically unused in industrial trucks of the known art so that the weight incorporated in the form of the moldings  10  can be used in its entirety as an additional counterweight.  
         [0027]      FIG. 2  is an overhead view which shows (left) an arrangement of two pressurized cylindrical tanks  3  which are surrounded by moldings  10 ,  15 , and (right) the same arrangement in an exploded view. The molding  15 , which is located between the two tanks  3 , has two recesses  16  with a circular or arc-shaped cross section, which are located between two parallel flat sides  17 . The moldings  10 , which are realized in the form of end pieces, are identical to the moldings  10  illustrated in  FIG. 1 . Additional tanks  3  can easily be inserted between the two tanks  3  by using additional moldings  15 . With the illustrated moldings  10 ,  15 , when standardized tanks  3  are used, a tank system of almost any desired arrangement and size can be constructed by using two types of moldings  10 ,  15 . An additional molding  19 , which fits the convex shape of a tank base  18  and fits between the moldings  10  and  15 , can be provided for the vicinity of the tank base  18 .  
         [0028]     If cylindrical tanks  3  of different lengths are provided, the moldings  10 ,  15  can be manufactured in the form of yard goods and cut to fit. It is also conceivable, however, that moldings  10 ,  15 , with a length that is less than or equal to the length of the shortest tank  3  being used, can be placed one behind another and cover tanks  3  of any desired length.  
         [0029]     Elastic support elements  20 , which can be made of rubber or a polymer material, for example, can be located in some or all of the recesses  11 ,  16 . These support elements  20  dampen impacts and vibrations. The wear of the tanks  3  and of the moldings  10 ,  15  is reduced because the tanks  3  and moldings  10 ,  15  are not in direct contact with one another and, therefore, cannot rub against one another. If the moldings  10 ,  15  are pressed against one another, the tanks are effectively prevented from moving in their longitudinal direction so that additional securing means are unnecessary.  
         [0030]      FIG. 3  is a schematic illustration of a molding  21  to hold four tanks  3  in a configuration that differs from the configuration illustrated in  FIG. 2 . In this case, not only can the tanks  3  be arranged in a linear row but a tank system can also be used that extends in two dimensions A, B and is stabilized by the arrangement of recesses  22  in the molding  21 . The arrangement can thereby be terminated by means of moldings  10  that are realized in the form of end pieces, one of which is shown in  FIG. 3 . The moldings  10 ,  15 ,  21  can be fastened to one another either by suitable fastening devices of the known art that are integrated into the moldings, such as threaded fasteners or slots or grooves and sliding blocks that are introduced into them, and/or by holding the moldings  10 ,  15 ,  21  together by means of straps, just to mention a few.  
         [0031]     It goes without saying that other realizations of the moldings  10 ,  15 ,  21  are conceivable, for example in the form of a molding that completely surrounds the tank  3 . In such an arrangement, the tank  3  is provided with optimal protection, although the installation and the replacement of the tank  3 , if necessary, are significantly more difficult compared to the illustrated variant. Depending on the specific requirements, the moldings  10 ,  15 ,  21  can be made of a ferrous material, such as grey cast iron, for example, or steel, and/or of lead or a lead alloy or another material of sufficiently high density. Lead and lead alloys are characterized by their high density and easy deformability. However, if the moldings  10 ,  15 ,  21  are required to absorb and/or transmit large forces, for example because additional components are fastened to them, a steel construction is preferable.  
         [0032]     It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Accordingly, the particular embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.