Patent Publication Number: US-11396445-B2

Title: Fork head with gripping device and lateral movement

Description:
FIELD OF THE INVENTION 
     The present invention relates to a fork head with a gripping device and lateral movement, especially designed to grip thin objects, such as, for example, the large shafts used in single-axis solar tracker apparatuses. 
     PRIOR ART 
     In different tasks, such as installing single-axis solar trackers, it is necessary to manipulate large objects the length of which is much greater than the transverse section thereof, such as the shafts used in single-axis solar tracker apparatuses, which, merely by way of reference, can be tubes wish a 150×150 mm square profile, with varying wall thicknesses of between 3 and 6 millimeters, and with lengths of up to 13 meters. Alternatively, the shafts used in single-axis solar tracker apparatuses may consist of round profile tubes or any other transverse sectional profile, whether regular or irregular. 
     To manipulate these types of thin objects, several people are required if the operation is done manually. When a lifting vehicle is used, such as a forklift with a fork head or the like, a special grip is necessary for holding and stabilizing the thin object to the fork head of the lifting vehicle. 
     CN 206901706 U discloses a fork head with a gripping and lateral movement device. The head includes a main frame intended to be fixed to a moving element of an elevator vehicle, a mobile frame movable by a first actuator along a transverse guide fixed to the main frame, two parallel fork arms fixed to the mobile frame, a gripping member pivotally mounted about a horizontal axis supported on the mobile frame, and a second actuator which pivots the gripping element relative to the mobile frame to trap a thin object in a hanging position between the gripping member and the two fork arms. 
     The gripping member described in said CN 206901706 U has a length in a direction transverse to the fork arms significantly shorter than the spacing between the two fork arms so that the gripping member can pass between the fork arms. This is a disadvantage since it can produce undesired bending deformations in the thin object when it is pressed by the gripping member at an intermediate point between two support points provided by the fork arms. 
     Accordingly, there is a need for a device that makes it possible to grip thin objects, such as tubes the length of which is much greater than the transverse section thereof, from a fork head of an elevator vehicle. There is also a need for a device that makes it possible to laterally move the gripping member together with the fork arms relative to a main frame of the head. 
     DISCLOSURE OF THE INVENTION 
     The present invention contributes to the above and other needs by providing a fork head with a gripping and lateral movement device for gripping thin objects, wherein the head comprises a main frame intended to be fixed to a moving element of an elevator vehicle, a mobile frame movable horizontally by a first actuator along a transverse guide fixed to the main frame, a fork having two parallel fork arms fixed to the mobile frame, and a gripping member mounted on the mobile frame and movable by a second actuator to and from the fork for trapping a thin object in a hanging position between the gripping member and the two fork arms. 
     The gripping member has a length in a transverse direction equal to or greater than a fork width defined as a distance between respective opposing outer edges of the two fork arms. Accordingly, the gripping member has end portions superimposed on to portions of the two fork arms. 
     With this arrangement, the thin object is pressed by the end portions of the gripping member against the corresponding portions of the fork arms, which ensures a firm and stable grip of the thin object without the grip producing bending stresses which can result in undesired deformations in the thin object. 
     In addition, the thin object, once gripped, can be moved laterally with respect to the main frame of the head by means of the first actuator, which facilitates precise positioning of the thin object via the lifting vehicle. 
     In a preferred embodiment the gripping member is movable along one or more linear guides fixed to the mobile frame, wherein the linear guides are perpendicular to a support member plane defined by upper surfaces of the two fork arms. The support member plane is usually horizontal or approximately horizontal and the linear guides are vertical or approximately vertical. 
     In a preferred embodiment, each of the linear guides is a guide having a guide body connected to the mobile frame and a telescoping rod connected to the gripping member and slidably inserted into the guide body. In an alternative embodiment the linear guides have a reverse arrangement in which the guide body is connected to the gripping member and the telescopic rod is connected to the mobile frame. Alternatively, any other guide device for the linear guides may be used. 
     Preferably, the first actuator is a first hydraulic cylinder having a cylinder body connected to the main frame and an extendable rod connected to the mobile frame. An inverse arrangement is equally possible in which the body of the first hydraulic cylinder is connected to the mobile frame and the extendable rod is connected to the main frame. Alternatively, any other type of motor associated with transmission of mechanical movement may be used for the first actuator. 
     Preferably, the second actuator or each second actuator is a second hydraulic cylinder having a cylinder body connected to the mobile frame and an extendable rod connected to the gripping member. An inverse arrangement is equally possible, in which the body of the second hydraulic cylinder is connected to the gripping member and the extendable rod is connected to the mobile frame. Alternatively, any other type of motor associated with transmission of mechanical movement may be used for the second actuator. 
     In an alternative embodiment, the gripping member is fixed to a movable arm having a pivotal movement about a horizontal axis, and the second actuator is a second hydraulic cylinder having a cylinder body connected to the mobile frame and an extendable rod connected to the movable arm or vice versa, or any other suitable motor means. 
     Preferably, the gripping member comprises a flat pressure plate parallel to the support member plane or a pressure plate configured in a direction parallel to the support member plane. In any event, the shape of the pressure plate is adapted to the particular shape of an outer surface of the thin object determined by the shape of the transverse sectional profile thereof. 
     Optionally, and in particular when the pressure plate is flat, the gripping member includes a leading skirt perpendicular to the pressure plate, and consequently perpendicular to the support member plane, extending downwardly from a forward transverse edge of the pressure plate. Optionally, the gripping member further comprises a rear rib extending upwardly from a rear transverse edge of the pressure plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The aforementioned and other features and advantages will be more fully understood from the following detailed description with no limiting effect of an example embodiment with reference to the accompanying drawings, wherein 
         FIG. 1  is a perspective view of a partial exploded view of a fork head with a gripping and lateral movement device for gripping thin objects in accordance with an embodiment of the present invention; 
         FIG. 2  is a perspective view of the assembled fork head of  FIG. 1  with a gripping member in an inactive position; 
         FIG. 3  is a perspective view of the fork head of  FIG. 2  with the gripping member in an active position gripping a thin object. 
         FIG. 4  is a front view of the fork head of  FIG. 2 ; 
         FIG. 5  is a partially sectioned bottom plan view of the fork head of  FIG. 2 ; 
         FIG. 6  is a transverse sectional side view of the fork head of  FIG. 2  with the gripping member in the inactive position; and 
         FIG. 7  is a transverse sectional side view of the fork head of  FIG. 2  with the gripping member in the active position gripping a thin object. 
     
    
    
     DETAILED DESCRIPTION OF AN EMBODIMENT 
     Referring first to  FIG. 1 , the reference sign  50  generally designates a fork head with a gripping and lateral movement device according to one embodiment of the present invention, which is intended to grip and manipulate objects in a stable and safe manner. The fork head  50  comprises a first subassembly  51  and a second subassembly  52 . 
     The first subassembly  51  of the fork head  50  includes a main frame  1  intended to be fixed to a mobile element of a lifting vehicle via anchors (not shown), a transverse guide  3  fixed to the main frame  1  and two fork arms  4   a ,  4   b  arranged so that they can be moved together along the transverse guide  3 . The fork arms  4   a ,  4   b  are parallel to a longitudinal direction X corresponding to a rear direction of the lifting vehicle and thus parallel to a direction of movement of the lifting vehicle. The transverse guide  3  is oriented in a transverse Y and horizontal direction y and perpendicular to the longitudinal direction X. 
     In the illustrated embodiment, the main frame  1  defines a peripheral frame having an upper bar  11 , a lower bar  12 , two end posts  13  and a central post  14  extending from the upper bar  11  to the lower bar  12 . The upper and lower bars  11 ,  12  are oriented in the transverse direction Y. The two end posts  13  and the central post  14  are oriented in a vertical direction Z perpendicular to the longitudinal direction X and to the transverse direction Y. The transverse guide  3  has two circular transverse sections extending from each of the end posts  13  to the central post  14 . 
     Each fork arm  4   a ,  4   b  is rigidly attached to one end of a respective vertical element  15  having at its other end a connecting element  16  provided with a circular opening through which the corresponding section of the transverse guide  3  is inserted so that the fork arms  4   a ,  4   b  can slide and pivot freely with respect to the transverse guide  3 . Between each fork arm  4   a ,  4   b  and the corresponding vertical element  15  thereof there is a curved transition section  17  that interferes with the lower bar  12  of the main frame to limit the pivoting of the fork arm  4   a ,  4   b.    
     The second subassembly  52  of the fork head  50  comprises a mobile frame  2  having an upper horizontal structure  18  and two rear posts  19  oriented in the vertical direction Z. The two rear posts  19  are fixed to the upper frame  18  engaging with braces  20 . Each of the rear posts  19  has a first bracket  21  configured to be attached to one of the vertical elements  15  which in turn are attached to the fork arms  4   a ,  4   b . Thus, the first subassembly  51  can slide and pivot together with the fork arms  4   a ,  4   b  along the transverse guide  3 . 
     Between the first subassembly  51  and the second subassembly  52  is a first actuator, which, in the illustrated embodiment, is comprised of a first hydraulic cylinder  7  having a cylinder body connected to a support member  22  which has a second bracket  23  fixed to the central post  14  of the main frame  1  and an extendable rod connected to one of the rear posts  19  of the mobile frame  2 . 
     Alternatively, the connection of the first hydraulic cylinder  7  could be reversed, i.e., with cylinder body connected to the rear post  19  and extendable rod connected to the support member  22 . 
     Both the first brackets  21  and the second bracket  23  include tightening screws by which it is possible to adjust the position of the second subassembly  52  relative to the first subassembly  51  in the vertical direction Z. 
     With this construction, activating the first hydraulic cylinder  7  moves the second subassembly  52  horizontally together with the fork arms  4   a ,  4   b  with respect to the main frame  1  of the first subassembly  51  along the transverse guide  3  parallel to the transverse direction Y. 
     The second subassembly  52  comprises a mobile gripping member  5  installed on the mobile frame  2  in a position facing the upper surfaces of the two fork arms  4   a ,  4   b  defining a support member plane. The gripping member  5  comprises a pressure plate  9  parallel to the support member plane. The pressure plate  9  has front and rear transverse edges parallel to the transverse direction Y. The gripping member  5  further comprises a front skirt  10   a  perpendicular to the pressure plate  9  which extends downwardly from the front transverse edge of the pressure plate  9  and a rear rib  10   b  extending upwardly from the rear transverse edge of the pressure plate  9 . 
     The gripping member  5  can be moved in the vertical direction Z along the linear telescopic guides  6  by means of second actuators, such as second hydraulic cylinders  8 . The linear guides  6  are perpendicular to the pressure plate  9  and consequently parallel to the vertical direction Z. Each of the linear guides  6  has a guide body connected to the mobile frame  2  and a telescopic rod slidably inserted into the guide body and connected to the gripping member  5 . The second hydraulic cylinders  8  have a cylinder body connected to the mobile frame  2  and an extendable rod connected to the gripping member  5 . 
     Alternatively, the connection of the linear guides  6  could be reversed, i.e., with the guide body connected to the gripping member  5  and the telescopic rod connected to the mobile frame  2 . Alternatively, the connection of the second hydraulic cylinders  8  could be reversed, i.e., with the cylinder body connected to the gripping member  5  and the extendable rod connected to the mobile frame  2 . 
     Thus, activating the second hydraulic cylinders  8  in a first direction causes a movement of the gripping member  5  toward the fork arms  4   a ,  4   b  by a path sufficient to trap a thin object  40  between the gripping member  5  and the two fork arms  4   a ,  4   b , the thin object  40  being arranged in a hanging position and oriented in a direction parallel to the transverse direction Y. Activating the second hydraulic cylinders  8  in a second opposite direction causes a movement of the gripping member  5  away from the fork arms  4   a ,  4   b  so as not to interfere with the thin object  40 . 
     Mounted on the upper frame  18  of the mobile frame  2  is a six-way valve  24  connected to the first hydraulic cylinder  7  and to the second hydraulic cylinders  8  via flexible conduits (not shown) connectable to a hydraulic system of the lifting vehicle. The operation of the first hydraulic cylinder  7  and the second hydraulic cylinders  8  is controlled via the six-way valve  24 . 
     As best shown in  FIGS. 3 and 4 , in any embodiment of the present invention the gripping member  5  has a length L in the transverse direction Y equal to or greater than a fork width W defined as a distance between respective opposite outer edges of the two fork arms  4   a ,  4   b  in the transverse direction Y and, and further the gripping member  5  has end portions  5   a ,  5   b  superimposed on portions of the two fork arms  4   a ,  4   b.    
     The term “thin object” is used in this description to mean an elongated object with a consistent transverse section with a large length relative to the size of its transverse section.  FIG. 3  shows the fork head of the present invention with the gripping member  5  in an active position gripping a thin object consisting of a square profile tube such as those used for example as turning shafts in single-axis solar tracker apparatuses. By way of reference, these square profile tubes can have a transverse sectional size of about 150×150 millimeters, with varying wall thicknesses of between 3 and 6 millimeters, and with lengths of up to 13 meters. Alternatively, the thin objects may consist of square, round or any other shape of regular or irregular transverse section.