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BACKGROUND OF THE INVENTION 
   The present invention relates to an adjustable-capacity bucket for backhoe or loader. 
   According to the prior art, buckets for backhoes or loaders applied to excavators, earth-movers or machines for moving materials in general have a structure that has a constant and non-modifiable capacity. 
   The main drawback that is observed with conventional buckets for backhoes or loaders is that since their capacity is not modifiable, machines with different capacities are needed for each individual different requirement. 
   This drawback entails cost burdens arising from the need to have multiple machines available, with considerable waste of time during work when a machine that is different from the one being used is needed due to suspension of work, the request for the appropriate machine, the wait for its delivery on site, and its installation. 
   These drawbacks have been overcome with the adjustable-capacity bucket for backhoe or loader according to the present invention. 
   OBJECTS OF THE INVENTION 
   The aim of the present invention is to provide a bucket for backhoe or loader that allows to adjust, on site and easily, its loading capacity according to the various requirements. 
   For this purpose, the present invention consists of an adjustable-capacity bucket for backhoe or loader, which is constituted partly by a fixed structure and partly by one or more movable members, which can slide on the fixed structure by means of adapted devices for mutual movement, so as to be able to adjust the width of the bucket and accordingly its capacity with simple operations. 
   To achieve the intended aim, according to a preferred embodiment, the adapted devices are constituted by pistons fixed both to the fixed structure and to the movable members so as to actuate their mutual movement. 
   In order to assist the pistons that actuate the movement of the movable members, sliding guides are arranged parallel to the direction of actuation of the pistons. 
   The fixed structure is substantially C-shaped and constitutes a rigid external member inside which one or more complementary movable members slide. 
   Some of the many advantages that are achieved with the present invention are the following. 
   The main advantage of the present invention is the great cost saving that is achieved by virtue of the possibility to deal with different needs by means of a single tool, by adjusting the breadth of the bucket, which allows to even double, and more than double, the loading capacity with a single machine. 
   A further advantage is the adaptability of the bucket even during work without unnecessarily wasting time. For example, to produce an excavation with a required cross-section and a width of 80 cm, it is possible to use a 60-cm bucket extended by 10 cm on each side. If a block or a loose shoulder is encountered during excavation, in order to widen the excavation it is not necessary to stop work to replace the bucket, but it is sufficient to actuate the widening of the bucket, deal with the critical situation, and then reduce again the width of the bucket in order to continue regularly with the excavation with required cross-section. 
   The fact that the structure of the bucket for backhoe or loader according to the invention is heavier than conventional ones is not a drawback, because the machine to which it is applied is always very heavy and the difference related to the weight of the bucket is not decisive. If deemed appropriate, it is always possible to ballast the machine additionally when it is necessary to move heavier loads. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     All of the advantages cited above and others will become apparent from the description of the following figures, which are provided merely by way of non-limiting example and wherein: 
       FIG. 1  is a view of a fixed structure with the frame for coupling to the excavator; 
       FIG. 2  is a view of a movable member applied to the fixed structure; 
       FIGS. 3 and 4  are respectively side views of the movable members; 
       FIGS. 5 and 6  are views of the profile of the movable members; 
       FIG. 7  is a front view of the backhoe bucket of  FIG. 2  in the closed position; 
       FIG. 8  is a front view of the backhoe bucket of  FIG. 2  in the open position; 
       FIG. 9  is a top view of the backhoe bucket of  FIG. 2  in the closed position; 
       FIG. 10  is a rear view of the backhoe bucket of  FIG. 2  in the closed position; 
       FIG. 11  is a perspective view showing only the fixed structure of a backhoe bucket, with the two movable members; 
       FIG. 12  is a side view of a loader bucket according to the invention; 
       FIG. 13  is a front view of the loader bucket of  FIG. 12  in the closed position; 
       FIG. 14  is a front view of the loader bucket of  FIG. 12  in the open position; 
       FIG. 15  is a perspective view showing only the rigid structure of a loader bucket, with a movable member; 
       FIG. 16  is a side view of a small backhoe bucket provided with two pairs of cylinders; 
       FIG. 17  is a sectional view of the backhoe bucket of  FIG. 16 ; 
       FIG. 18  is a front view of the backhoe bucket of  FIG. 17  shown in the open position; 
       FIG. 19  is a view, similar to  FIG. 18 , but showing the backhoe bucket in the closed position; 
       FIG. 20  is a plan view of the backhoe bucket of  FIG. 19 ; 
       FIG. 21  is a rear view of the backhoe bucket of  FIG. 20 ; 
       FIG. 22  is a side view of a medium backhoe bucket provided with three pairs of cylinders; 
       FIG. 23  is a sectional view of the backhoe bucket of  FIG. 22 ; 
       FIG. 24  is a front view of the backhoe bucket of  FIG. 23 , shown in the open position; 
       FIG. 25  is a view, similar to  FIG. 24 , but showing the backhoe bucket in the closed position; 
       FIG. 26  is a plan view of the backhoe bucket of  FIG. 25 ; 
       FIG. 27  is a rear view of the backhoe bucket of  FIG. 26 ; 
       FIG. 28  is a side view of a large backhoe bucket provided with four pairs of cylinders; 
       FIG. 29  is a sectional view of the backhoe bucket of  FIG. 28 ; 
       FIG. 30  is a front view of the backhoe bucket of  FIG. 29 , shown in the open position; 
       FIG. 31  is a view, similar to  FIG. 30 , but showing the backhoe bucket in the closed position; 
       FIG. 32  is a plan view of the backhoe bucket of  FIG. 31 ; 
       FIG. 33  is a rear view of the backhoe bucket of  FIG. 31 ; 
       FIG. 34  is a side view of a loader bucket provided with three pairs of cylinders; 
       FIG. 35  is a sectional view of the loader bucket of  FIG. 34 ; 
       FIG. 36  is a front view of the loader bucket of  FIG. 35 , shown in the open position; 
       FIG. 37  is a view, similar to  FIG. 36 , but showing the loader bucket in the closed position; 
       FIG. 38  is a plan view of the loader bucket of  FIG. 37 ; 
       FIG. 39  is a rear view of the loader bucket of  FIG. 38 . 
   

   In the various figures, similar elements have been designated by the same reference numerals. 
   DETAILED DESCRIPTION 
   In  FIG. 1 , the reference numeral  10  designates the bucket frame for anchoring to the arm of the excavator (not shown in the drawings), with which conventional backhoe and loader buckets are usually provided. 
   The pins for fixing to the excavator pass through the holes  11  and  12 . 
   According to the invention, a fixed structure  17  is connected rigidly to the frame  10 , is substantially C-shaped and is preferably obtained by means of a solid and/or box-like bent metal plate, in order to give it great rigidity and strength. 
   The movable members, which are suitable to slide within the fixed structure  17 , allow to vary the loading capacity of the bucket by virtue of their sliding. The movable members also are preferably provided by means of a metal plate bent into a C-shape and their external contour is complementary to the internal contour of the fixed structure  17 . 
   The movable members are connected to the fixed structure  17  by means of actuators constituted for example by pistons, where the term “piston” is used to designate the assembly constituted by a cylinder, a piston and the corresponding rod. 
     FIG. 2  illustrates a movable member  13  applied to the fixed structure  17 . 
   According to a particular example of embodiment, the internal movable members are two,  13  and  14 , and are shown individually in  FIGS. 3 and 4 . The movable members are mirror-symmetrically identical except for a protruding wing, designated by the reference numerals  18  and  19 . These wings  18  and  19  are meant respectively to connect the movable members  13  and  14  to the fixed structure  17 . 
   The pistons, which are two in the example of  FIG. 2  and are designated by the reference numerals  15  and  16 , are fixed by means of the cylinder to the fixed structure  17 , and the rod is fixed respectively to the protruding wings  18  and  19  at the holes  35  and  36 . The two pistons  15  and  16  are mutually parallel and work so as to generate movement in two mutually opposite directions. 
   The wings  18  and  19  have different contours or shapes so as to allow both the coupling of the stem of the corresponding piston and leave free the space for the movement of the opposite stem and the coupling of the corresponding two sliding guides. 
   In the illustrated example, there are two sliding guides for each movable member, respectively  20  and  21  for the movable member  13  and  22  and  23  for the movable member  14 . 
   Holes  30  and  31  for the passage of the guides  20  and  21  are provided on the wing  18  of the movable member  13 , and holes  32  and  33  for the passage of the guides  22  and  23  are formed on the wing  19  of the movable member  14 . Similar corresponding holes  40 ,  41 ,  42 ,  43  are provided on the fixed structure  17 , which is shown in  FIG. 1 . 
   The side view of  FIG. 2  illustrates the movable member  13 , with the wing  18  that allows the coupling of the piston  16  and of the guides  20  and  21 . 
     FIGS. 5 and 6  illustrate the profile of the movable members  13  and  14 , with the wings  18  and  19  in which the axes of the holes are indicated. 
     FIG. 7  is a front view of the backhoe bucket, with the movable members  13  and  14  in the closed position. 
   Likewise,  FIG. 8  is a front view of the backhoe bucket with the movable members  13  and  14  in the open position. In the open position, the guides  20  and  22 , which protrude beyond the fixed structure  17 , become visible. 
   The two pistons  15  and  16  are visible in the top view of  FIG. 9 , are connected respectively to the two wings  18  and  19 , and act in opposite directions. The upper sliding guide  20 , connected to the wing  18  of the movable member  13 , can also be seen. 
   The rear view of  FIG. 10  shows the rear guides  21  and  23  and the piston  16 . 
     FIG. 11  is a perspective view of the fixed structure  17 , with the two movable members  13  and  14 , in which the member  13  is shown in the closed position, contained within the fixed structure  17 , while the member  14  is shown in the open, i.e., extended, position, outside the fixed structure  17 . 
     FIGS. 12 ,  13 ,  14  and  15  illustrate an example of embodiment of the invention applied to a loader bucket. The operating principle is in fact similar and only the detail of the coupling to the machine is different. 
   The same reference signs already used for the backhoe bucket have been adopted, with the only addition of a prime sign. 
     FIG. 12  is a side view of a loader bucket according to the invention. It can be seen that the only substantial difference with respect to the backhoe bucket is the different position of the frame  10 ′ for the loader bucket. Indeed, instead of being located above the backhoe bucket, the frame  10 ′ is arranged behind the loader bucket. Accordingly, the configuration of the fixed structure  17 ′, of the wings  18 ′, and the arrangement of the pistons  16 ′ and of the guides  20 ′ and  22 ′ changes, but the basic principle remains unchanged. 
     FIG. 13  is a front view of the loader bucket of  FIG. 12  in the closed position and  FIG. 14  is a front view of the loader bucket of  FIG. 12  in the open position;  FIG. 15  is a perspective view showing only the rigid structure  17 ′ of a loader bucket, with a single movable member  13 ′. The reference numeral  24  designates the arm of the loader to which the frame  10 ′ is connected. 
   The pistons are connected to the excavator by means of supply or hydraulic lines. 
     FIGS. 16-21  illustrate a small backhoe bucket, generally designated by the reference numeral  1 , which is characterized by the presence of two pairs of actuation cylinders or pistons, designated by the reference numerals  101  and  102  respectively. 
     FIGS. 22-27  illustrate a medium backhoe bucket, generally designated by the reference numeral  2 , which is characterized by the presence of three pairs of actuation cylinders or pistons, respectively designated by the reference numerals  201 ,  202  and  203 . 
     FIGS. 28-33  illustrate a large backhoe bucket, generally designated by the reference numeral  3 , characterized by the presence of four pairs of actuation cylinders or pistons, designated by the reference numerals  301 ,  302 ,  303  and  304  respectively. 
     FIGS. 34-39  illustrate a loader bucket, generally designated by the reference numeral  4 , which is characterized by the presence of three pairs of actuation cylinders or pistons, designated by the reference numerals  401 ,  402  and  403  respectively. 
   The field of the present invention also includes an embodiment with a different number of sliding guides and/or pistons, a different arrangement or size thereof, and regardless of the way in which they are actuated, for example hydraulic or oleo pistons, pneumatic pistons, electric pistons, et cetera. 
   These characteristics in fact depend on the requirements of the market, of manufacture and of use, and on the size of the backhoe bucket or loader bucket. Furthermore, variations that have a different number of movable members and can be widened for example telescopically or in concertina fashion are understood to be also included. 
   Finally, the pistons can be replaced with other movement tools, such as chains, worm screws, belts or the like, anchored to the fixed structure and to the movable members. 
   The present invention includes all the detail variations and modifications that might be obvious to the person skilled in the art and are not beyond the scope of the present invention but are understood to be included within the scope of the claims that follow.

Summary:
A bucket or scoop with adjustable capacity has a fixed structure which forms an external rigid element and also has one or several mobile elements, complementary to the fixed structure, which slide inside the same by means of special devices. The special devices are actuators or pistons fixed either to the fixed structure or to the mobile elements, to occasion a reciprocal movement thereof. Sliding guides are arranged parallel to the direction of action of the pistons.