Abstract:
A hydraulic steering actuator system for a forklift with front and rear sections includes a hydraulic steering motor. The forklift front section includes a mast mounting a pair of fork blades and a pair of wheels. The forklift rear section mounts a pair of drive wheels. The forklift front and rear sections are connected by an articulated connection with a vertical rotational axis. The steering actuator motor driveshaft extends along the vertical rotational axis. First and second actuator mounting brackets are connected to the forklift front and rear sections respectively. One of the mounting brackets includes upper and lower locking assemblies locking the hydraulic steering motor driveshaft whereby torque applied to the steering motor is transmitted to the articulated connection for turning the forklift front section relative to the forklift rear section. The range of motion is preferably 180°-205° for accommodating side-loading operations from relatively high storage shelves.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of and claims the benefit of U.S. patent application Ser. No. 12/962,444, filed Dec. 7, 2010, now U.S. Pat. No. 8,276,704, which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present disclosed technology relates generally to a system for steering and operating forklift trucks, and more specifically to steering and operating a narrow-aisle, articulated forklift truck using a hydraulic actuator. 
         [0004]    2. Description of the Related Art 
         [0005]    A typical narrow-aisle articulated forklift truck (or “forklift”) comprises front and rear chassis sections each having a pair of wheels on a respective common axis. The rear wheels provide drive-motion to the forklift truck, while the front wheels are non-driven and steer the truck. The chassis sections are pivoted together about a vertical axis so that the front chassis section, including a mast, can be turned at an angle of approximately 90° each way (preferably 180°-205° total range of movement) relative to the rear chassis section to allow the truck to insert loads into, and remove loads from, the faces of the aisle. 
         [0006]    Without limitation on the generality of useful applications of the present invention, an exemplary use consists of loading and unloading palletized inventory in narrow-aisle facilities, such as warehouses. Steering with the front wheels is generally preferred for such applications because rear-wheel steering forklifts generally have relatively large turning radii and are thus ill-suited for loading and unloading storage bins in narrow aisles, such as those found in many warehouses and other storage facilities. Narrow-aisle, articulated forklift trucks, on the other hand, allow the mast-portion of the forklift to turn independently from the body of the truck, which allows the operator to load or unload material positioned perpendicular to the aisle along which the truck is traveling. Typical narrow-aisle trucks are capable of rotating the front chassis mast section at least 90° each way relative to a direction of travel along a warehouse shelf aisle. 
         [0007]    A problem condition associated with many previous articulated forklift trucks is the articulating joint between the front and rear chassis sections. An electric or hydraulic motor is typically used to steer the forklift truck by rotating the front chassis section relative to the rear section. Because the front chassis includes the mast, which is subjected to heavy loads, the rotation motor and connection are high-wear components which can be expensive to replace. What is needed is an articulated forklift truck capable of maneuvering in narrow aisles and handling heavy loads while minimizing the wear on the articulating component of the truck. 
         [0008]    Heretofore there has not been a forklift truck embodying the capabilities of the invention presented herein. 
       SUMMARY OF THE INVENTION 
       [0009]    Disclosed herein in an exemplary embodiment is a narrow-aisle articulated forklift truck including front- and rear-chassis portions. A hydraulic actuator capable of allowing rotation through approximately 180°-205° joins the two portions and is capable of absorbing the high-wear forces of loads applied to the front-chassis portion. 
         [0010]    The hydraulic actuator provides a connection between the front and rear chassis portions, allows the front-chassis portion to rotate about the actuator, and provides a means for hydraulic power to pass through the actuator to the forklift truck mast, allowing the mast to tilt and the fork to raise and lower while protecting the hydraulic hoses. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The drawings constitute a part of this specification and include exemplary embodiments of the disclosed subject matter illustrating various objects and features thereof, wherein like references are generally numbered alike in the several views. 
           [0012]      FIG. 1  is an isometric view of an articulated forklift with a hydraulic steering actuator comprising a preferred embodiment of the present invention. 
           [0013]      FIG. 2  is a side elevational view of the preferred embodiment of the present invention. 
           [0014]      FIG. 3  is a top-down plan view of the preferred embodiment of the present invention demonstrating the rotational capabilities of the front-chassis portion. 
           [0015]      FIG. 4A  is an isometric view of the hydraulic steering actuator. 
           [0016]      FIG. 4B  is another isometric view of the hydraulic steering actuator. 
           [0017]      FIG. 5A  is an exploded isometric view of the hydraulic steering actuator and a mounting bracket used for connecting the actuator to the front-chassis portion of the forklift. 
           [0018]      FIG. 5B  is another isometric view of the hydraulic actuator and the mounting bracket shown in  FIG. 5A . 
           [0019]      FIG. 6  is a sectional view of the hydraulic actuator taken generally a long line  6 - 6  in  FIG. 5B . 
           [0020]      FIG. 7  is an elevational view showing the connection of the mounting bracket and the hydraulic actuator in the direction of arrow  7  in  FIG. 6 . 
           [0021]      FIG. 8A  is an exploded isometric view of the hydraulic actuator and the mounting block used for connecting the actuator to the rear-chassis portion of the forklift. 
           [0022]      FIG. 8B  is an isometric view of the hydraulic actuator and mounting block of  FIG. 8A . 
           [0023]      FIG. 9  is a side elevational view of the connection of the mounting block and the hydraulic actuator. 
           [0024]      FIG. 10  is an upper, isometric view of a three-wheel forklift comprising an alternative aspect of the invention. 
           [0025]      FIG. 11  is an enlarged, isometric view of the alternative aspect forklift, particularly showing the front wheel and the base of the mast. 
           [0026]      FIG. 12  is a front elevational view of the alternative aspect forklift with the mast turned approximately 90°. 
           [0027]      FIG. 13  is a side elevational view of the alternative aspect forklift. 
           [0028]      FIG. 14  is a top plan view of the alternative aspect forklift. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     I. Introduction and Environment 
       [0029]    As required, detailed aspects of the disclosed subject matter are disclosed herein; 
         [0030]    however, it is to be understood that the disclosed aspects are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art how to variously employ the present invention in virtually any appropriately detailed structure. 
         [0031]    Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, up, down, front, back, right and left refer to the invention as oriented in the view being referred to. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the embodiment being described and designated parts thereof. Forwardly and rearwardly are generally in reference to the direction of travel, if appropriate. Said terminology will include the words specifically mentioned, derivatives thereof and words of similar meaning 
         [0032]    A preferred embodiment of the present invention is an articulating forklift truck  2  comprised of a front-chassis portion  5  and a rear-chassis portion  3 . The forklift truck  2  is designed to operate along narrow aisles by loading inventory or items located perpendicular to the forklift truck&#39;s path. The front-chassis portion  5  and the rear-chassis portion  3  are joined at a pivot point formed by a hydraulic actuator  8  bolted to a mounting block  78  and a mounting bracket  10 . An example of a suitable hydraulic actuator  8  includes the T20 Series Hydraulic Actuator manufactured by Helac Corporation of Enumclaw, Washington. Such a hydraulic actuator  8  operates as a complete steering and bearing system in a single, rugged component. The actuator  8  is adapted for handling the high-wear loads placed upon it when inventory is lifted by the forklift truck  2 . 
       II. Articulating Forklift Truck  2   
       [0033]    Referring to the drawings in more detail, the reference numeral  2  generally refers to the articulating forklift truck used for loading and unloading inventory along narrow aisles. Articulating forklift trucks are used in such circumstances because the front-chassis portion  5  of the forklift truck  2  is capable of rotating 90° or more to the right or the left of the path traveled by the forklift truck. The forklift mast  6  and the fork blades  4  are mounted to the front-chassis portion  5  and, when rotated, can lift or unload inventory without adjusting the travel path of the forklift truck  2 . 
         [0034]      FIGS. 1-3  generally show an articulating forklift truck  2  in a preferred embodiment, including the front-chassis portion  5  and the rear-chassis portion  3 . The rear-chassis portion  3  is further comprised of an operator&#39;s seat  20 , a roll cage  22 , steering controls (steering wheel)  24  and mast and fork controls  26 . A mounting block  78  with upper and lower mounting flanges  80 ,  81  is located below the operator&#39;s seat  20  and the steering controls  24 . A steering and control subsystem  12 , a hydraulic subsystem  13 , and a computer processer  14  are mounted within the rear-chassis  3  for coordinating control signals from the operator to the forklift truck  2 . For example, the hydraulic steering and control subsystem  12  can differentially drive the rear wheels  15  for effectively operating the forklift  2  in a zero turning radius (“ZTR”) mode of operation. Thus, the forklift front portion  5  can be advanced towards a line of shelves even when the front wheels  17  are turned at 90° right angles to the longitudinal axis. The control subsystem  12  can automatically meter hydraulic fluid to the steering actuator  8  and otherwise control the drive train of the forklift  2  in various operating modes, such as straight-line driving, turning and store-and-retrieve warehouse shelving procedures. 
         [0035]    The front-chassis portion  5  is further comprised of a mast  6  and forks  4  vertically adjustably mounted thereon. A fork cable assembly  30  is mounted atop the mast  6  and connected to the forks  4 . The cable assembly  30  is controlled via the fork controls  26  and is capable of raising and lowering the fork  4  along the mast  6 . A mounting bracket  10  is connected to the rear of the mast  6 . Two mast tilt hydraulic cylinders  28  are mounted on either side of the mounting bracket  10  and connected to the mast  6 . The tilt cylinders  28  allow the mast  6  to be tilted forward or backwards, allowing positioning of the forks  4 . 
         [0036]    A central portion  7  joins the front-chassis portion  5  to the rear-chassis portion  3 . The central portion  7  is comprised primarily of a hydraulic actuator  8  bolted to the mounting block  78  and the mounting bracket  10 . A sensor system  31  is attached to the mounting block  78  and the hydraulic actuator  8  and includes a rotation sensor  16  for determining the rotation degree of the front-chassis portion  5  relative to the rear-chassis portion  3 , and a hydraulic sensor  18  for determining the tilt of the mast, along with the other hydraulic functions of the forklift truck  2 . 
         [0037]    As shown in  FIG. 3 , the front-chassis portion  5  is rotatable about the hydraulic actuator  8 . The rotation radius R indicates the rotational path of the front-chassis portion  5  as it rotates about the hydraulic actuator  8 . The rotation path allows for at least a 90° rotation of the front-chassis portion  5  to either side of the forklift truck  2  longitudinal axis. 
         [0038]      FIGS. 4A and 4B  show the hydraulic actuator  8  in more detail. The actuator  8  is comprised of an actuator body  36 , an actuator upper flange  40 , a lower flange  41 , and a rotator shaft  38 . Each actuator flange  40 ,  41  includes a hydraulic inlet/outlet port  34  and a plurality of bolt holes  32 . The bolt holes  32  allow the actuator  8  to be physically bolted to the mounting block  78  via a plurality of mounting bolts  54 . 
         [0039]    The upper actuator flange  40  includes a first port  42 , and the lower actuator flange  41  includes a second port  43 . The first and second ports  42 ,  43  include plugs which can be loosened and tightened to adjust the rotation angle of the actuator. When constructing the forklift truck  2 , the plugs located in the first and second ports  42 ,  43  are loosened. The actuator  8  is rotated 90° so that it is perpendicular to the mounting bracket  10 . The plugs located in the first and second ports  42 ,  43  are then re-tightened. This allows the forklift front chassis portion  5  to rotate through 180° or more for sideloading capability. 
         [0040]      FIGS. 5A-7  show the connection of the hydraulic actuator  8  to the mounting bracket  10 . As shown in  FIG. 5A , the mounting plate  10  is further comprised of a bracket plate  44  including a lower mounting projection  60  with a lower mounting projection opening  66 , a bracket base protrusion  64  with a bracket base protrusion opening  70 , four tilt-hydraulic connection flanges  50  each including a hinge receiver  52 , two recesses  46  each including two hydraulic access receivers  48 , and four bolt-holes  58 . An upper mounting projection  62  includes an upper mounting projection opening  68  which receives the upper stem of the hydraulic actuator rotator shaft  38 . An upper locking assembly  72  secures the upper mounting projection  62  to the hydraulic actuator  8 . 
         [0041]    The upper mounting projection  62  bolts to the bracket plate  44  via four mounting bolts  54  and associated washers  56 . The lower stem of the rotator shaft  38  is secured within the lower mounting projection opening  66  with a lower locking assembly  74 . As shown in  FIG. 5B , with the hydraulic actuator  8  mounted to the mounting bracket  10 , the hydraulic inlet/outlet ports  34  are accessible facing out from the bracket  10 . A tilt hydraulic cylinder  28  is connected to each pair of connector flanges  50  via a hinge connection  76 . 
         [0042]      FIGS. 8A-9  demonstrate the connection of the hydraulic actuator  8  to the mounting block  78 . As shown in  FIG. 8A , the mounting block  78  includes an upper mounting flange  80  and a lower mounting flange  81 , each including a plurality of bolt holes  82  and a hydraulic port access  84 . Mounting bolts  54  connect the hydraulic actuator  8  to the mounting block  78  through the flange bolt holes  82  and the actuator bolt holes  32 . A sensor system  31  comprising a sensor body  86  and a sensor arm  88  is mounted to the top face of the mounting block  78 . The arm  88  interacts with the hydraulic actuator  8  to determine the rotation angle of the actuator  8 . 
         [0043]    As shown in  FIGS. 8B and 9 , hydraulic hoses  90  are fed through the hydraulic port accesses  84  and connected to the hydraulic actuator&#39;s hydraulic inlet/outlet ports  34 . The hydraulic hoses  90  connect to the hydraulic subsystem  13  located in the rear-chassis portion, and travel through the actuator  8  to the various hydraulically powered components located in the front-chassis portion  5 . 
       III. Operation of the Hydraulic Steering Actuator  8  and the Forklift Truck  2   
       [0044]    In an embodiment of the present invention, an operator positioned in the operator&#39;s seat  20  in the rear-chassis portion  3  controls the motion of the forklift truck  2  by powering the rear wheels  15 . Using the steering controls  24 , the operator turns the front-chassis portion  5  by rotating the hydraulic actuator  8 , turning the front wheels  17  and directing the forklift truck  2  in the process. 
         [0045]    The operator also controls the tilt of the mast  6  and the lift of the fork  4  using the fork controls  26 . The tilt of the mast  6  is controlled through the hydraulic system. The hydraulic hoses  90  connect to the hydraulic actuator  8 , from which the hydraulic tilt cylinders  28  are fed. These hydraulic cylinders  28  allow the entire mast  6  and the fork  4  to tilt away from or towards the rear-chassis portion  3  of the forklift truck  2 . If the operator requires the fork  4  to be maneuvered beneath a piece of inventory, the operator can tilt the mast and the fork  4  forward, guide the truck toward the object, and then tilt the mast  6  and the fork  4  backwards, resulting in the inventory object being lifted from the ground and onto the fork  4 . 
         [0046]    The rotator shaft  38  of the hydraulic actuator  8  is drivingly connected to and causes the front-chassis portion  5  to rotate according to the steering wheel movements by the operator. The upper and lower locking assemblies  72 ,  74  create a rigid connection between the rotator shaft  38  and the upper  62  and lower  60  mounting projections of the mounting bracket  10 . An example of the locking assemblies  72 ,  74  is the Ringfeder Locking Assembly RfN 7013 manufactured by Ringfeder GMBH of Germany. The forklift front wheels may optionally turn in the same direction as the actuator rotator shaft  38  to assist in turning the forklift truck  2 . 
         [0047]    A forklift truck comprising a modified or alternative aspect of the present invention is shown in  FIGS. 10-14  and is generally designated by the reference numeral  102 . The forklift truck  102  is similar to the forklift truck described above, except that a single forward wheel  117  is provided on a front chassis portion  105  mounting a mast  106 , in lieu of the forward wheels  17  mounted on the front chassis portion  5  described above. The three-wheel configuration of the forklift truck  102  provides different operating characteristics, such as a shorter overall length with the mast  106  turned 90°, as shown in  FIGS. 10-14 . Moreover, the three-wheel configuration effectively utilizes the load-distributing configuration provided by the single forward wheel  117  in cooperation with the rear wheels  115 , which form a load-bearing triangle defined by the relative positions of the three wheels. Another advantage relates to accommodating uneven and out-of-level operating surfaces, upon which the three-wheel forklift truck  102  can effectively balance and distribute the weight. An actuator  108  operates in a similar manner to the actuator  8  described above. 
         [0048]    It will be appreciated that the articulated forklift truck can be used for various applications not described herein. Moreover, the articulated forklift truck can be compiled of additional elements or alternative elements to those mentioned herein, while providing similar results.