Patent Publication Number: US-7913792-B2

Title: Electric fork-lift truck and process for manufacturing the same

Description:
The present invention relates to an electric fork-lift truck. Furthermore, the invention relates to a process for manufacturing the same. 
     A known electric fork-lift truck mainly comprises a unitized body and a so-called “mast”, arranged in the front side of the unitized body. 
     The unitized body, equipped with a safety roof, includes the passenger compartment for the operator with related controls, circuits and control means, as well as compartments for housing the electric battery and the ballast. Furthermore, one or more rear, directional wheels with possible motor means and motion-transmitting means, in case of rear-wheel driven or four-wheel driven truck, are connected to the unitized body. 
     The mast substantially includes a stiff rectangular supporting and guiding frame, extended in height and in case extensible vertically, and a slide sliding in vertical direction along said frame and bearing a pair of front forks, arranged in a plane essentially orthogonal to said frame, for gripping and supporting the load to be moved. The mast bears on the lower side the truck&#39;s two front wheels, coaxial therebetween, with possible motor means and motion-transmitting means in case of front-wheel driven or four-wheel driven truck. The mast is articulated with respect to the front part of the body in order to oscillate around a transversal axis substantially parallel to the one of the front wheels. Such oscillation is called “swinging” of the mast. The swinging is controlled by means of one or more operating cylinders, articulated at one end with respect to the body and at the other end with respect to the mast, around the respective transversal axes parallel to the articulation one of the mast. 
     For example, in case of a fork-lift truck with three wheels (thereof two front wheels and one rear wheel) and rear-wheel driven, the mast is articulated to the body by means of a transversal axis placed at intermediate height of the body, whereas the articulation axis of the operating cylinders with respect to the mast is substantially arranged in the base area or lower crosspiece of the latter. By means of such arrangement, the swinging operation allows to sensibly vary the pitch or wheelbase between the front wheels and the rear wheel or wheels, by correspondingly varying the centre of gravity of the load brought on the truck forks. Upon increasing the pitch, the front wheels move forward with respect to the body and the mast tilts slightly by approaching its upper crosspiece to the roof of the body: the load increases the truck stability. On the contrary, when the pitch between the wheels is reduced and the mast is made to swing forwards, the truck stability is guaranteed by the ballast. 
     In case, instead, of a fork-lift truck with three wheels (thereof two front wheels and one rear wheel) and front-wheel driven, the mast—which supports the driving wheels and the related motor and transmission means—is articulated with respect to the body around a transversal axis arranged near the wheel axis, whereas the articulation axis of the operating cylinders with respect to the mast is placed over the mast&#39;s articulation axis with respect to the body. In this case, the swinging operation cannot be performed by varying sensibly the pitch between the truck&#39;s wheels, thus loosing the advantages illustrated above. 
     Constructively, for each model of fork-lift truck it is possible assembling several types of masts, according to the operations to be carried out. However, as the front wheels are carried by the mast, the both front-wheel driven and rear-wheel driven truck can be finished only once the articulated connection of the mast with respect to the unitized body has occurred. Therefore, if one wish subsequently to change the mast—for example with another much higher one—it is necessary to disassemble not only the mast, but also the related motor and transmission means, with considerable technical and economical costs. 
     Furthermore, in order to meet the orders of potential customers, it is necessary to store a great number of wholly finished trucks with masts of different kinds, that is alternatively it is necessary to wait for the order of each customer in order to implement the truck according to his/her needs. 
     The present invention, starting from knowing such inconveniences, wishes to solve them. 
     An object of the present invention is to provide an electric fork-lift truck wherein the pitch or wheelbase between the front wheels and the rear one or ones can be varied, in order to swing the mast and this with front-wheel, rear-wheel or four-wheel drive. 
     Another object of the present invention is to provide an electric fork-lift truck with variable pitch between front and rear wheels, the structure thereof with related driving and idle wheels is independent from the mast, so as to allow the interchangebility of the mast itself in a simple and quick way. 
     Still another object of the present invention is to provide an electric fork-lift truck with variable pitch between front and rear wheels which can be implemented as autonomous and semi-movable structural unit, without the related mast, in order to ease the storage and the transportation and to allow assembling the mast of the wished type at time of choosing by the end user. 
     An additional object of the invention is to provide a process for producing an electric fork-lift truck with variable pitch between front and rear wheels, to allow implementing an autonomous and semi-movable structural unit, without the related mast, in order to ease the storage and the transportation and to allow assembling the mast of the wished type at time of choosing by the end user. 
    
    
     
       The present invention will better result from the following detailed description by referring to the enclosed drawings, provided by only way of example and not for limitative purposes, wherein: 
         FIG. 1  is a three-quarter perspective, front view of an electric fork-lift truck with three wheels according to an embodiment of the present invention; 
         FIG. 2  is a view similar to that of  FIG. 1 , wherein, however, apart from other parts, also the mast&#39;s forks and the wheels are omitted, for illustrating clarity; 
         FIG. 3  shows, in an exploded perspective view, the truck of  FIG. 2  with the mast separated from the body of the truck itself; 
         FIG. 4  is a perspective view similar to that of  FIG. 3 , wherein, however, between the body and the mast also an intermediate frame is illustrated in exploded view; 
         FIG. 5  is a top plan view, in different scale, of the truck of  FIG. 1 ; 
         FIG. 6  is a section view according to line A-A of  FIG. 5 , showing the mast in an oscillating position swinging rearwards; 
         FIG. 7  is a view similar to that of  FIG. 6 , but showing the mast in oscillating position swinging forwards; 
         FIG. 8  is an exploded perspective view and in greater scale of said intermediate frame with two idle wheels; 
         FIG. 9  is an exploded perspective view and in greater scale of said intermediate frame with two driving wheels and related motor and transmission means; 
         FIGS. 10 ,  11 ,  12  are views of said intermediate frame, respectively in back, side and plan elevations; 
         FIG. 13  is a section view in greater scale according to line XIII-XIII of  FIG. 10 ; 
         FIG. 14  is a three-quarter perspective, front view of the unitized body of the truck of  FIG. 1 , with related controls, circuits and control means and equipped with rear wheel and said intermediate frame with driving front wheels, implemented as autonomous and semi-movable structural unit, without the related mast. 
     
    
    
     In the drawings, said three-wheel electric fork-lift truck is indicated as a whole with  10  ( FIG. 1 ). 
     Said truck  10  comprises a unitized body  11  and a mast  12  ( FIG. 3 ). 
     The unitized truck  11  is equipped with a safety roof  11 . 1  and includes, in a way known on itself and not further described, the operator compartment with related controls, hydraulic and electric circuits and control means, as well as the compartments housing the electric battery and the ballast. 
     The lateral sides  11 . 2  of the body  11  have, on the front side, a box-like body, by providing on the lower side respective wheelhouses  11 . 21  and contain a front plate  11 . 3  therebetween, partially re-entered the body and delimiting the lower area of the passenger compartment on the front side. 
     The mast  12  includes a stiff rectangular frame  12 . 1 , equipped with two parallel vertical longitudinal members  12 . 2 , extended in height and extensible vertically by means of an additional frame sliding along the longitudinal members themselves. A slide  13  is mounted on said shaft  12  sliding in vertical direction and bears a pair of front forks  13 . 1  ( FIG. 1 ) arranged in a plane essentially orthogonal to said frame  12 . 1 , for gripping and supporting the load to be moved. 
     According to the invention, a stiff intermediate frame  14  is arranged oscillating between the sides  11 . 2  of the body  11 , in the front of said front plate  11 . 3 . 
     Said frame  14  comprises ( FIGS. 4 ,  8 - 13 ) two longitudinal members  14 . 1  mainly vertical in stamped plate, an upper crosspiece  14 . 2  with metallic cylindrical body, prolonged beyond the longitudinal members  14 . 1  by means of respective heads with reduced diameter  14 . 21  and a lower crosspiece  14 . 3  in metallic plate with box-like body opened on the rear side and parallel to the upper crosspiece. The heads  14 . 21  of the upper crosspiece of said frame  14  are housed freely rotating in respective bushes (known on themselves and not illustrated) fixed coaxially according to a transversal horizontal axis X-X ( FIG. 3 ), in respective holes  11 . 22  (thereof only one is visible in the drawings) provided in said sides  11 . 2  of the body  11 , so that said frame  14  can oscillate around said axis itself. The upper crosspiece  14 . 2  of the frame  14  is placed below the top of the front plate  11 . 3 , whereas its lower crosspiece  14 . 3  is placed substantially in the compartment between the wheelhouses  11 . 21  of the body  11 , without interfering with the same wheelhouses. 
     The longitudinal members  14 . 1  at the level of the lower crosspiece  14 . 3  have respective plate-like extensions  14 . 10  ( FIG. 8 ), extended on the rear side according to respective planes orthogonal to the axis X-X. In said extensions  14 . 10  respective through holes  14 . 11  are provided for the assembly of corresponding bushes (known on themselves and not illustrated) aligned according to a horizontal transversal axis Y-Y, parallel to said axis X-X. Above said holes  14 . 11 , respective notches  14 . 12 , opened upwards, are provided in the extensions  14 . 10 . Furthermore, on opposite sides with respect to said notches  14 . 12 , two through holes  14 . 13  for assembly screws or bolts are provided in each extension  14 . 10 . 
     Besides, respective through holes  14 . 14  for assembly screws or bolts are provided in the top area of said longitudinal members  14 . 1 , whereas two through holes  14 . 30  for assembly screws or bolts are provided in the crosspiece  14 . 3 . It will be noted that the axes of the holes  14 . 14  are parallel to the axis Y-Y, whereas those of the holes  14 . 30  are orthogonal to a plane passing through said axis itself. 
     In the intermediate axis  14  two idle wheels  21  are assembled coaxially therebetween, according to said axis Y-Y, housing the respective axes  21 . 1  within said bushes fastened in the holes  14 . 11  and by fixing to said frame  14  the respective supporting plates  21 . 2  by means of screws or bolts passing in the holes  14 . 13  and in corresponding holes  21 . 3  provided in said supporting plates  21 . 2  themselves. Said idle wheels  21  are arranged at the wheelhouses  11 . 21  of the body  11 . 
     Alternatively ( FIG. 9 ), in said intermediate frame  14  two individually motorized driving wheels  22  are assembled in a way wholly similar to said idle wheels  21 . It will be noted that, in this case, the notch  14 . 12  of the extension  14 . 10  of each longitudinal member  14 . 1  houses a part of the geared-motor group MR associated to each driving wheel  22  so that said extension  14 . 10  acts as a holder of said geared-motor group MR. Also said driving wheels  22  are arranged at the wheelhouses  11 . 21  of the body  11  ( FIG. 14 ). 
     A hydraulic operating cylinder  30  ( FIGS. 6 ,  7 ) is articulated with respect to the body  11 , in the lower side and with the axis arranged in the longitudinal vertical median plane of the same, by means of a pin  31  with axis parallel to the axis X-X, whereas the stem thereof  30 . 1  is articulated to said intermediate frame  14  by means of a pin  32  with axis parallel to said axis X-X too. Said pin  32  is fastened between two vertical tongues  33  ( FIGS. 10-13 ), welded inside the box-like lower crosspiece  14 . 3  of said intermediate frame  14 . Said intermediate frame  14  can be then made to oscillate around said axis X-X by extending and retracting the stem  30 . 1  with respect to the hydraulic cylinder  30 , which is operatively connected in the hydraulic circuit of the truck. 
     As it appears from above and as illustrated in  FIG. 14 , the unitized body  11  with (driving or idle) rear wheel and with intermediate frame  14  equipped with (idle  21  or driving  22 ) front wheels constitutes a structurally autonomous and semi-movable unit  40 , suitable for the storage and the transportation. 
     Besides, the longitudinal members  12 . 2  of the frame  12 . 1  of the mast  12  have respective supporting and anchoring rear fixed arms  12 . 3  (FIGS.  3 , 4 ) with ends with downward-opened hook and arranged at a height substantially corresponding to the one of the upper crosspiece  14 . 2  of the frame  14 , once the mast  12  is assembled in the truck  10 . Furthermore, two supporting brackets  14 . 31  ( FIGS. 8 ,  9 ) project frontally on the lower side of the lower crosspiece  14 . 3  of the frame  14  and bear respective assembly pins  14 . 32  oriented upwards. Two corresponding assembly fixed joints (which cannot be seen in the drawings) are provided in the lower crosspiece of the frame  12 . 1  of the mast  12 . By means of such arrangement the easy assembly of the mast  12  in said structural unit  40  can be performed in the following way: said mast  12  is shown with the back portion thereof opposed to the intermediate frame  14  assembled in the front portion of the body  11 , by making the vertical pins  14 . 32  of said intermediate frame  14  to engage within the corresponding assembly fixed joints provided in the lower crosspiece of the frame  12 . 1  of said mast, whereas the supporting and anchoring arms  12 . 3  of the mast itself engage from the top and partially wind the upper crosspiece  14 . 2  of said intermediate frame  14 . Then, the mast  12  is fastened with respect to said intermediate frame  14 , by clamping screws or bolts the shanks thereof are arranged to pass, on one side, through the assembly holes  14 . 14  in the longitudinal members  14 . 1  of the intermediate frame  14  and corresponding holes in said mast and, on the other side, through the holes  14 . 30  in the lower crosspiece  14 . 3  of said intermediate frame  14  and corresponding holes in said mast. 
     With reverse operation, the disassembly of said mast  12  is performed. 
     The mast  12  thus results to be easily disassembled for maintenance or replacement by other mast. 
     Said mast  12 , once assembled, can be made to oscillate integrally with said intermediate frame  14  around the axis X-X by means of said operating cylinder  30  so as to perform the forward and rearward swinging, according to need. Such operation can be carried out with both idle  21  and driving  22  front wheels. 
     The process for manufacturing the fork-lift truck according to the invention mainly comprises the following steps:
         assembly of the idle  21  or driving  22  front wheels of the truck onto the intermediate frame  14 , in the last case the wheels being equipped with the respective motor and motion transmission means MR;   assembly of the intermediate frame  14  in the lower portion of a unitized body  11 , assembled and equipped at least with a directional rear wheel and with the related controls, circuits and control means, by means of housing the heads  14 . 21  of the upper crosspiece thereof  14 . 2  in corresponding bushes, fastened coaxially, according to said transversal horizontal axis X-X ( FIG. 3 ), in the respective holes  11 . 22  provided in the sides  11 . 2  of the body  11 , so that said frame  14  can oscillate around said axis itself;   assembly of the operating cylinder  30 , which is connected on one side to the body  11  and on the other side to said intermediate frame  13 , in the lower areas of the same, in an articulated way around respective axes  31 ,  32  parallel to said axis X-X,
 
thus implementing a structurally autonomous and movable/semi-movable unit (for example, the unit  40  of  FIG. 14 ), suitable for the storage and the transportation, and a final step for assembling in a dismountable way said mast  12  onto said intermediate frame  14 .
       

     In particular, this last step is carried out in the following way: 
     said mast  12  is shown with the back portion thereof opposed to the intermediate frame  14  assembled in the front portion of the body  11 , by making the vertical pins  14 . 32  of said intermediate frame  14  to engage within the corresponding assembly fixed joints provided in the lower crosspiece of the frame  12 . 1  of said mast, whereas the supporting and anchoring arms  12 . 3  of the mast itself engage from the top and partially wind the upper crosspiece  14 . 2  of said intermediate frame  14 . Then, the mast  12  is fastened with respect to said intermediate frame  14 , by clamping screws or bolts the shanks thereof are arranged to pass, on one side, through the assembly holes  14 . 14  in the longitudinal members  14 . 1  of the intermediate frame  14  and corresponding holes in said mast and, on the other side, through the holes  14 . 30  in the lower crosspiece  14 . 3  of said intermediate frame  14  and corresponding holes in said mast. 
     ADVANTAGES OF THE INVENTION 
     As it results from above, the present invention allows achieving the objects illustrated in the premises. 
     In particular, the electric fork-lift truck, according to the invention:
         allows varying the pitch or wheelbase between the front wheels and the rear one or ones in order to swing the mast, both front-wheel and rear-wheel or four-wheel driven,   comprises a structure with related driving or idle wheels, independent from the mast, so as to allow the assembly, the disassembly or the interchangeability of the mast itself in an easy and quick way;   is implemented as an autonomous and movable/semi-movable structural unit, without the related mast in order to ease the storage and transportation thereof and to allow assembling the mast of the wished type at time of choosing by the end user.       

     Furthermore, the process for manufacturing the truck according to the invention makes easier the operations for manufacturing the truck and allows implementing an autonomous and movable/semi-movable structural unit, without the related mast so as to ease the storage and transportation thereof and to allow assembling the mast of the desired type at time of choosing by the end user.