Device for cutting angular profiles applicable to hydraulic shears
BACKGROUND OF THE INVENTION 
     The present invention relates to a device for cutting angular profiles, the device particularly being applicable to hydraulic shears. 
     The object of the device of the invention is to cut angular profiles, i.e. members having an angular transverse cross-sectional configuration, without producing any deformation or loss of material. The device of the invention comprises a plate, acting as the knife bearer, mounted on a shaft about which it can make partial reciprocating turns by means of a hydraulic pressure cylinder. 
     The main feature of the invention resides in the original structure and in the arrangement of the knife with respect to the mentioned plate, so that during angular movement of the plate, the knife which cuts the angular profiles moves in a direction such that the cutting edges thereof are always parallel to the wings of the profiles. Thus, a clean cutting of the profile takes place, i.e. without deformation or loss of material. 
     This is very important since deformation and loss of material do occur when using known hydraulic shears due to the following: 
     In one type of hydraulic shear the material is deformed since the knife is mounted on the knife bearing plate in a fixed and rigid manner. Thus, the knife follows the angular movement of the plate and, naturally, it does not extend parallel on the profile to be cut. 
     In another type of hydraulic shear the material to be cut is lost since the knife, in order to facilitate cutting, has an angle greater than 90°. Besides, this type of shear has two knives, one at each side of the knife cutter, with a separation equal to the thickness of the knife cutter, and it is precisely this which causes a portion of the material to be lost during cutting. 
     SUMMARY OF THE INVENTION 
     In the case of the present invention, deformation and loss of material do not take place due to the specific characteristics of the knife and to the way in which the knife is mounted on the knife bearing plate. 
     The cutting device of the invention is characterised in that it comprises a plate, generally triangular in shape, a rear surface of which has a prismatic projection corresponding to one of the sides thereof. The prismatic projection, and consequently the side where such projection is located, is arched and adjusts to a complementary recess provided for such purpose in the front surface of the knife bearing plate. 
     Furthermore, the knife is positioned between a pair of guides provided in the body of the machine. In this way, i.e. due to this original arrangement of the knife with respect to the knife bearing plate and due to the triangular shape thereof, when the mentioned knife bearing plate is moved in an angular direction, by means of a corresponding hydraulic pressure cylinder, the knife or triangular cutting plate is displaced in a linear direction following the bisecting line of the angle which is established by the cutting edges thereof, thereby proportioning a cut without deformation and without any loss of material since it rests on an angular profile to be cut, maintaining constant parallelism between the cutting edges thereof and the wings of the profile. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the structural characteristics and the functioning of the device of the present invention, reference will now be made to the accompanying drawings, wherein: 
     FIGS. 1 and 2 respectively are a front elevational view and a longitudinal sectional view of a knife bearing plate according to the invention. 
     FIG. 3 is a front view of the assembly of the device including the bearing plate and a triangular knife supported thereby; and 
     FIGS. 4 and 5 are cross-sectional views taken along lines III--III and IV--IV, respectively, of FIG. 3. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As can be seen, the device of the present invention comprises a plate 1 acting as a knife bearer and which is mounted to the general frame of the machine, through a hole 2, on a shaft about which the plate can make partial reciprocating turns by means of a hydraulic pressure cylinder, the rod 3 of which is represented in FIG. 3. 
     At the front surface of this plate 1 there is installed a knife 4 which is a plate, generally triangular in shape, the posterior or rear part of which has a prismatic projection 5 which follows an arched or curved path to be adjusted in a complementary recess 6 made for such purpose in the knife bearing plate 1, thus enabling relative movement along the complementary curves between plate 1 and knife 4. 
     The cutting edges 7 of the knife 4 form a straight dihedral and are positioned parallel to the cutting edges of a counterknife 8. Between this counterknife 8 and the knife 4 there is formed, in the knife bearing plate 1, a hollow or aperture 9 through which the angular profiles to be cut pass. 
     The vertices or corners 10 of the triangular plate or knife 4, common to the arched side and respective edges 7 thereof, are bevelled to be in sliding contact with guides 11 solidly attached to the body of the machine. Thus, due to angular movement of the knife bearing plate 1 about the shaft 2 by means of the pressure cylinder 3, the knife 4 cuts an angular profile or member inserted in the hollow 9. Arrow A indicates the radial movement which the knife 4 is necessarily forced to make due to the presence of the guides 11 which, as explained, are solidly attached to the body of the machine. In this way, when the knife 4 presses the angular profile to be cut, the cutting edges 7 are maintained parallel to the cutting edges of the counterknife 8 and also to the wings of the angular profile which is cut without deformation or loss of material.