Not applicable.
The invention relates to a material handling vehicle, and more particularly, to a material handling vehicle configured to contain hydrogen for operation with a hydrogen fuel cell power system.
Material handling vehicles, for example, fork trucks, pallet trucks, order pickers, and the like, are routinely used in various industries to move nearly all types of product. Many of these vehicles incorporate electric power systems, which offer certain advantages because they can be recharged using available electric power supplies. Electric power systems, however, have several drawbacks. Recharging and replacing batteries, for example, is time consuming and requires specialized equipment, which can both increase the vehicle downtime and overall cost of operating the vehicle.
Hydrogen fuel cell power systems have been incorporated into vehicles in an effort to eliminate the inefficiencies of the typical electric power system that draws power only from onboard batteries. In a hydrogen fuel cell power system, hydrogen stored onboard of the vehicle is routed to multiple fuel cells in a fuel cell stack where the hydrogen is manipulated to create an electric current. The electric current is used to charge onboard batteries and power other electronic components. Simplistically, fuel cells use hydrogen and oxygen to create an electric current by separating electrons from hydrogen molecules and routing the electrons through an electrical circuit. The electron deficient hydrogen molecules are then recombined with the electrons and oxygen molecules to form water. The creation of an electric current onboard by the fuel cell eliminates long battery recharge time and the need routinely to manipulate bulky batteries. Thus, hydrogen fuel cell power systems reduce or eliminate many of the drawbacks of conventional electric power systems.
Storing ample hydrogen for the fuel cell on the material handling vehicle, however, presents a practical problem. In comparing typical gasoline and hydrogen systems, when gaseous hydrogen is pressurized to 5,000 pounds per square inch, twelve times more volume is required to store the equivalent amount of energy found in conventional gasoline. Increasing the storage pressure of hydrogen to 10,000 pounds per square inch reduces the volumetric ratio to a still significant eight to one. As a result, storing a sufficient amount of hydrogen onboard the vehicle to meet or exceed the operating parameters of fossil-fuel based systems presents a significant impediment to the design and widespread adoption of hydrogen fuel cell systems.
Previous inventions have attempted to retrofit fuel cell assemblies, including hydrogen storage tanks or pressure vessels, into the preexisting battery compartment space. In these vehicles, however, the mass of the retrofit fuel cell assembly is typically significantly less than the mass of the battery it is replacing—undesirably altering the vehicle dynamics. Furthermore, because the battery compartment space is relatively small, the amount of work that a vehicle can perform before needing to refill the hydrogen storage (i.e., duty cycle) is inadequate for many applications, especially as compared to traditional power systems.
In light of the above, a need exists for a material handling vehicle having onboard hydrogen storage that increases the hydrogen storage capacity without significantly altering the dynamics of the material handling vehicle.
The present invention addresses all of the above needs, and more, with material handling vehicles that maximize the space within and around the vehicle for the storage of hydrogen. The material handling vehicles in accordance with the invention incorporate hydrogen storage with the mast, overhead guard, and/or chassis, where applicable. The present invention makes the use of hydrogen fuel cell powered vehicles practical by, among others, extending the vehicle duty cycle, maintaining operator visibility, and preserving vehicle dynamics. It is of note that the invention is equally applicable to hybrid power systems wherein hydrogen storage needs are present in addition to more traditional fuels such as propane.
In one embodiment, the present invention includes a material handling vehicle having a mast for manipulating a load. The mast comprises a tank configured to contain hydrogen. A fuel cell is coupled to the tank for receiving hydrogen from the tank and converting the stored hydrogen to an electric current.
In another embodiment, the invention includes a material handling vehicle comprising an overhead guard. The overhead guard includes a tank configured to contain hydrogen. A fuel cell is coupled to the tank for receiving hydrogen from the tank and converting the hydrogen to an electric current.
In yet another embodiment, the present invention includes a material handling vehicle comprising a chassis having a tank configured to contain hydrogen. A fuel cell is coupled to the tank for receiving hydrogen from the tank and converting the hydrogen to an electric current.
The foregoing and other advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings that form a part hereof and in which there is shown, by way of illustration, example embodiments of the invention. These example embodiments, however, do not necessarily represent the full scope of the invention and reference must be made to the claims for determining the scope of the invention.
The present invention is applicable to all material handling vehicles and industrial trucks including, but not limited to, fork trucks, order pickers, pallet trucks, tow tractors, stackers, swing reach/turret trucks, sideloaders, and counterbalanced trucks; however, the example embodiment will be described with specific reference to the forklift truck 10 shown in
Referring to
Hydrogen is stored onboard of the forklift truck 10 in a pressure vessel or tank and is coupled to the fuel cell 18 to create an electric current. The electric current created by the fuel cell 18 is typically coupled to the battery 20 where the charge is stored until needed to operate the forklift truck 10 (e.g., propel the drive wheels 24, raise the mast assembly 14, power operator instrumentation 21, and the like). The general components and operation of a hydrogen fuel cell forklift truck 10 are well known to those skilled in the art. Therefore, the remaining description focuses on the new and useful hydrogen storage of the present invention.
Hydrogen may be stored in liquid form, gas form, combined with a solid hydrogen carrier, or some combination thereof. In dealing with material handling vehicles, e.g., a forklift truck 10, the two general categories of high mass and low mass storage systems must be considered so as to maintain and/or improve the dynamics of the material handling vehicle.
High mass systems incorporate materials such as steel tanks or solid hydrogen carriers (e.g., metal hydrides and the like). Due to the substantial mass added by these systems, each application requires specific analysis to determine the strategic placement of the tank and associated components to optimize each material handling vehicle.
Low mass systems include the use of lighter tank materials, such as, composite tanks, small diameter stainless steel tubing (typically less than three inches in nominal diameter), or liquid tanks. As opposed to high mass systems, low mass systems and tanks do not require significant alteration of a material handling vehicle because the dynamic effects of the low mass system are minimal. However, given the particular placement and capacity of the low mass system, the dynamics of the material handling vehicle may require application specific analysis to keep a material handling vehicle's center of gravity low, maintaining the desired stability of the vehicle.
The center of gravity of a material handling vehicle, regardless of incorporation of a high mass or low mass system, is preferably maintained low and centered within the vehicle. Altering the distribution of mass of a material handling vehicle with low, centered, vertically hung stationary masses requires less dynamic consideration than symmetric lateral and fore/aft alterations to the same vehicle. Further, any asymmetric alterations that affect the center of gravity of a material handling vehicle (especially on high-lift trucks wherein the load being manipulated may be suspended a significant distance from the main body of the material handling vehicle) require a more in-depth review to ensure that the functionality and capabilities of the material handling vehicle remain at desired levels. Such lateral and fore/aft changes require consideration and evaluation on an application-by-application basis.
Although varying by application, in an exemplary embodiment, the weight of hydrogen stored in the various configurations is unlikely to exceed approximately eleven pounds; thus, the weight fluctuation as hydrogen is consumed during operation will have little influence on the overall center of gravity and dynamics of the material handling vehicle.
In accordance with the invention, a hydrogen tank may be configured with the mast 14, the overhead guard 16, and/or the chassis 12 of the forklift truck 10, collectively the “components.” In each configuration, the hydrogen tank(s) are operationally coupled to the fuel cell 18 and the tank(s) may be coupled to, integral with, and/or housed within, the various components (i.e., mast 14, overhead guard 16, and/or chassis 12). Many tank-component combinations exist. In one non-exhaustive example configuration, a first tank may be integral with the mast 14, a second tank may be coupled to the overhead guard 16, and a third tank may be housed within the chassis 12, all within one material handling vehicle. Any one of the tank-component combinations is within the scope of the present invention.
In one example embodiment, hydrogen storage may be provided in conjunction with the mast assembly 14. As more clearly shown in
The depicted mast assembly 14 represents only one of the numerous mast assemblies to which the present invention is applicable. For example, integrated masts (i.e., where the rams for actuating the mast are also structural members) and mono masts (i.e., where the masts consists of a single support mast) are viable alternative configurations.
As previously mentioned, hydrogen is stored in a tank 36 that can be configured with the mast assembly 14 in several ways. Generally, the tank 36 may be coupled to the mast assembly 14, integral with the mast assembly 14, and/or housed within the mast assembly 14. Each of the variations will be described below in turn.
With reference to
The tanks 36 may be coupled adjacent the mast assembly 14 in various ways. For example, the tanks 36 of the example embodiment are coupled to the base members 28 with straps 38 secured to the base members 28 with bolts 40. Other coupling mechanisms, such as ratchet straps, are available to secure the tanks 36 to the mast assembly 14 during operation of the forklift truck 10. In general, the dynamic nature of the tanks 36 must be taken into consideration, in addition to the typical lack of suspension on material handling vehicles, when designing the coupling system for each tank 36. Any straps, bands, brackets, adhesives, welds, pins/hinges, and/or foam encasements should allow for some freedom for expansion and contraction, bending, and torsion of the materials and tanks 36 without fatiguing the coupling. Isolation mounts (not shown) or other absorption materials may be included to reduce the vibrations transferred to or between tanks 36. Additional considerations for environmental effects should be incorporated. For example, a material handling vehicle that routinely operates in and out of a freezer requires couplings that allow for cyclical expansion and contraction of components.
The tanks 36 are preferably coupled to the base member 28 of the mast assembly 14 because the base members 28 are stationary and do not extend and retract during operation of the forklift truck 10. However, with the appropriate couplings between tanks 36, tanks 36 may be secured to other or multiple members of the mast assembly 14, such as the outer telescoping member 30 and the inner telescoping member 32. Additional center of gravity benefits are achieved by keeping the tank 36 mass substantially at or below the collapsed height of the forklift truck 10. Securing tanks 36 to the upper members (e.g., the outer telescoping member 30 and the inner telescoping member 32) of the mast assembly 14 raises the center of gravity of the forklift truck 10 and requires that the counterbalance mass 19 increases accordingly, especially when a high mast or a high mass system is used.
The hydrogen within the tank 36 is expelled out of control valve 42 and through lines 44 where it preferably combines with a tank 36 coupled to the other base member 28 of the mast assembly 14. A pressure regulator 45 is placed in the lines 44 to maintain an appropriate pressure as the hydrogen flows to the fuel cell 18. The lines 44 are preferably hard-plumbed stainless steel lines, but may be flexible lines and the like. Alternatively, each tank 36 may be plumbed to a common rail (not shown) where the pressure of the hydrogen is regulated and monitored. While a single or multiple pressure regulators 45 may be placed anywhere along lines 44, the pressure regulator 45 is preferably placed downstream of the common rail at or near the location of the fuel cell 18. All of the various example embodiments are plumbed and coupled to the fuel cell 18 in a similar manner.
The specifics of hydrogen storage and delivery are well known to those having ordinary skill in the art. However, in regards to material handling vehicles, several items are of note due in part to the dynamic, unsuspended nature of most material handling vehicles and the small size of hydrogen molecules. Fittings should be avoided where possible in place of welded joints. Further, where fittings and joints are used, they should be located in areas that are easily checked for leakage and, should a leak occur, be vented to the atmosphere to prevent the buildup of hydrogen in a confined volume.
The tanks 36 in this example embodiment are typical pressure vessels used to store fluids (e.g., gases and liquids) under pressure. Typical tanks 36 are produced from steel, but may be of a lighter or heavier material to reduce or increase the amount of mass added to the mast assembly 14. The tanks 36 may be capable of being replaced by removing the straps 38 or the tanks may be refilled via control valve 42 or a separate hydrogen port (not shown) connected so as to allow all of the tanks 36 to be refilled from one convenient location. Additionally, the tank 36 need not extend the length of the mast assembly 14, several shorter tanks 36 may be attached to the mast assembly 14 and plumbed together using conventional techniques.
Tanks 36 may be cast, rolled, formed, and the like. The storage method desired, be it liquid, solid, or gas, and the size of the tank 36 will generally define the material the tank 36 is made of. A small diameter tube shaped tank 36 would generally be produced from stainless steel. When the liquid form of hydrogen is used, a substantial insulative layer must be included. Furthermore, despite that pressure vessels and tanks 36 are typically rounded, non-curved tanks 36 (e.g., square, rectangle, triangular, and the like) are possible given the appropriate design considerations (stresses, pressures, etc.), especially for relatively small tanks 36. Lastly, the stresses imparted by welding of small and relatively thin walled tanks 36 requires significant design consideration to ensure the proper operation of the tank 36.
Another way in which hydrogen is stored in a tank configured with the mast assembly 14 requires that the tanks be integral with the members of the mast assembly 14. In this scenario, the members of the mast assembly 14 define the tanks 36 and thus directly store the hydrogen. The tanks 36 are designed taking into account the traditional requirements of pressure vessels, in addition to ensuring the proper clearances for expansion and contraction of the pressurized portion of the tank 36 to allow the forklift truck 10 to operate as desired.
Turning briefly to
Turning to
Several of the available mast assembly 14 member cross-sections (e.g., base member 28) are illustrated in
Application requirements, vehicle dynamics, and pressure vessel design are considered to create a particular tank 36. For example, only the lower portion of the base member 28 may be configured as a tank 36 where the vehicle dynamics dictate a lower center of gravity. The materials and dimensions are influenced by such factors as the required internal pressure of the tank 36 and susceptibility of the tank 36 to vibration. Additionally, if the tank 36 needs to be replaced, ease of removal from the mast assembly 14 should be considered.
In yet a further example, the tank 36 may be housed within the mast assembly 14. Turning to
Ballast 54 may be included to at least partially surround the tanks 36. The ballast 54 may be an insulative material such as a polymer, rubber, foam, and the like, insulating the tanks 36 from vibration, shock, and the ambient environment. Where liquid hydrogen is stored in the tanks 36, the ballast 54 may include the appropriate insulation to maintain the desired storage parameters.
Turning briefly to
Each of these hydrogen storage techniques may be combined to obtain the most efficient result given the specifics of the application. Certain configurations may be preferred where additional ballast 54 is required due to the dynamics of the forklift truck 10. For example, only the lower portion of the base member 28 of the mast assembly 14 may contain ballast 54 comprising concrete, steel shot, and the like to keep the forklift truck 10 center of gravity low.
We turn our attention to a second example embodiment of the present invention in which hydrogen is stored in conjunction with the overhead guard 16 shown in
With reference to
However, turning to
Referring again to
Configuring tanks 36 in the overhead guard 16 creates additional forklift truck 10 dynamic considerations. By adding mass to the overhead guard 16, the center of gravity of the forklift truck 10 is raised, lessening the stability of the forklift truck 10. To help compensate, ballast 54 may be added to the lower portions of the overhead guard 16 (or another portion of the forklift truck 10) or low mass systems principles may be used (e.g., composite tanks) in the overhead guard 16. In one example, the ballast 54 may comprise a solid hydrogen carrier configured to supply hydrogen to the fuel cell 18.
A third example embodiment of the present invention includes hydrogen storage configured with the chassis 12. Again, all of the above considerations (e.g., plumbing configuration, tank materials, vehicle dynamics, and the like) are equally applicable to the third example embodiment wherein the chassis 12 forms the basis for hydrogen storage.
As with the mast assembly 14 and the overhead guard 16, the tank of the chassis 12 may be coupled to the chassis 12, integral with the chassis 12, and/or housed within the chassis 12. The term “chassis” is used broadly to encompass, at a minimum, the members making up the frame of the vehicle (here a forklift truck 10) and the structure surrounding an operator area.
Turning to
The tank 36 may be integral with the chassis 12 as shown in
Turning to
The tanks 36, as described in relation to any embodiment, are preferably made of 316L stainless steel and may of varying dimensions. Table A lists some of the possible tank 36 dimensions and approximate hydrogen storage capacities when the tank 36 takes the general form of a tube.
Table B lists some of the possible tank 36 dimensions and approximate hydrogen storage capacities when the tank 36 takes the general form of a rectangle or square, more typically found in the chassis 12 or overhead guard 16.
Turning to
An example assembly 124 of tanks 36 is shown in
With additional reference to
The tank 36 configuration may be designed to fit within, couple to, or form integrally with at least one member of the mast assembly 14, the overhead guard 16, and/or the chassis 12. The compact arrangement of the tubing 128 increases the mass of the tank 36 and thus reduces the need for additional ballast, however, ballast may be incorporated if a particular application will benefit. In one preferred form, the length L (shown in
Given the benefit of this disclosure, one skilled in the art will appreciate the many tube 128 configurations available in light of specific application requirements. For example, with reference to
Table D lists example tube 128 dimensions and tank 36 capacities when the tank 36 is configured generally as shown in
Preferred example embodiments of the present invention have been described in considerable detail. Many modifications and variations of the preferred embodiment described will be apparent to a person of ordinary skill in the art. Therefore, the invention should not be limited to the embodiments described.
This application claims priority to U.S. provisional application No. 61/017,286 filed Dec. 28, 2007, which is hereby incorporated by reference as if fully set forth herein.
Number | Date | Country | |
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61017286 | Dec 2007 | US |