Self-centering device for quick hooking and release of farm tools provided with a hydraulic hoister
BACKGROUND OF THE INVENTION 
     The present invention relates to a self-centering device for quick hooking and release of farm tools onto and off a tractor provided with a hydraulic hoister. 
     More particularly, the invention relates to a device of the above kind that allows one to remarkably improve the hooking and release of farm tools to the tractor provided with a hydraulic hoister. 
     Today, for this kind of work, rather complex apparatuses exist. These apparatuses do not allow one shot hooking. 
     At present, the main drawback is due to the fact that the tractor driver in order to hook the tool on the three usual hooking points is obliged, if alone, to get on and to get off more than once from the driving seat and to make numerous adjustment of the coupling devices. 
     Further, the worker must perform a certain number of operations in order to put the tractor and the tool along the same axis, said tool having previously been left (at the moment of releasing after the previous use) conveniently in a flat position. Otherwise, it is necessary to manually arrange the same with the consequent drawbacks due to the remarkable weights and to the often asymmetrical constructive shapes. 
     Thus, summarizing, the present hooking requirements often necessitate the presence of two workers, introduce the risk of injuries, involve a remarkable waste of time (four or five minutes or even more), and require a great deal of manipulation to place the tool both horizontally and vertically aligned with the tractor. 
     SUMMARY OF THE INVENTION 
     The device proposed according to the present invention eliminates the above drawbacks, provoking the coupling of the tool by the simple lifting of the tractor hydraulic hoister, even if the two elements are not perfectly aligned on the same plane (the solution allows a misalignment of up to 11 degrees) and laterally out of alignment (even of an angle of 18 degrees). 
     Further, the solution according to the invention, employing a third hooking hydraulically adjustable point, allows for an out of plane angle, acceptable for the hooking operation, of up to 30 degrees or more. 
     It is therefore a specific object of the present invention to provide a self-centering device for quick hooking and release of farm tools onto and off of a tractor provided with a hydraulic hoister. In so doing, the present invention comprises a first substantially triangular male element, preferably coupled to said tractor, a second substantially triangular female element, preferably coupled to said farm tool to be hooked, said first and second substantially triangular elements being coupable to each other in a fixed joint relationship by the effect of the weight of the same tool to be hooked, coupling and releasing means of said two elements of the present invention also being provided so as to be operable directly from the tractor such that the driver need not get on and off the tractor as in the prior art. 
     Preferably, according to the invention, said first and second substantially triangular elements employ C-sectioned bars, having an opened wing arrangement with one element featuring a pair of the C-sectioned bars coupled by electrowelding. 
     Further, according to the invention, said first substantially triangular element is coupled to the tractor by three fixing plates. 
     Still according to the invention, said second substantially triangular element is coupled to the tractor by three fixing plates. 
     Still according to the invention, said second substantially triangular element is coupled to the tool to be hooked and released by three couplings, particularly adapter bolted plates and/or pins. 
     Always according to the invention, said coupling and releasing means can be made up of a latch pin provided on said first substantially triangular element. 
     There can further be provided a series of adaptor universal plates and/or bolted extensions, which allow for the use of the device with any brand, kind and size of tractor, having any power, and the application to any farm tool having standard couplings of the different sizes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described for illustrative, but not limitative purposes, according to its preferred embodiments, with particular reference of the figures of the enclosed drawings, wherein: 
     FIG. 1 is a top view of the second element of the device according to the invention; 
     FIG. 2 is a top view of the first element of the device according to the invention; 
     FIG. 3 is a section view along line 3--3 of FIG. 1; 
     FIG. 4 is a view from the direction of line 4--4 of FIG. 2; 
     FIG. 5 is a section view along line 5--5 of FIG. 1; 
     FIG. 6 is a section view along line 6--6 of FIG. 2; and 
     FIG. 7 is a section view along line 7--7 of FIG. 4; 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Observing now the figures of the enclosed drawings, it can be noted that the device according to the invention is made up of two coupling triangular elements 1 (FIG. 1) and 2 (FIG. 2), realized by employing &#34;C&#34; shaped section bars having opened wings (see sections 5--5 and 6--6--respectively FIGS. 5 and 6), of 510 type steel, with one of the elements featuring a pair of facing C-shaped section bars coupled by electrowelding. 
     If the section bars have a tubular shape, obviously it is not necessary for electrowelding. 
     The triangular element 2 provided with male section bars is previously mounted on three points of the tractor hoister (not shown) by fixing plates 3, 4 and 5. 
     In view of the reduced dimensions, the triangular element 1 need not be removed in order to allow the coupling of fittings not employing the hoister (for example the trailer or the transport trolley). 
     The triangular element 1 having receiving or female section bars must be suitably prearranged on the tool couplings 6, 7 and 8, by suitable adapter bolted plates and/or pins (not shown); in order to obtain the maximum functionality. In view of the low costs and the simplicity of the present invention&#39;s design, each tool (plow, harrow, etc.) can be provided with a fixed female 1, element permanently mounted. 
     At the moment of use of the device, it is sufficient to bring the tractor near to the tool, to lift the hoister until provoking the fixed coupling of the two triangular elements 1 and 2 and the lifting from the ground of the same tool, which in view of the particular shape of the section bars, will be self-centering on the male triangular element 2 coupled to the tractor. 
     In order to complete the hooking, the tractor driver, without getting off from the vehicle, will couple a latch pin 9 (see FIGS. 4 and 7) provided above on the triangular male element 2, and that will block the female triangular element 1 on the male 2, until when making the opposite operation on the latch 9 and making the contrary operations previously described, the tool will be released from the tractor. 
     The particular shape of the section bars of the elements 1 and 2 (section 5--5 and 6--6, FIGS. 5 and 6) guarantees the stiffness and the strength of the coupling. 
     To complete the full functionality of the device according to the invention, there is provided a series of adapter plates (not shown), allowing for universal use of the invention with all kinds of tractors and tools. 
     The present invention has been described for illustrative, but not limitative purposes, according to its preferred embodiments, but it is to be understood that modifications and/or changes can be made by those skilled in the art without departing from the relevant scope as defined in the enclosed claims.