Clamping device for removably securing shaping moulds on the plates of moulding presses
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a clamping device for removably securing shaping moulds on the plates of moulding presses. 
     2. History of the Invention 
     In order to removably secure each of the two elements of a shaping mould on one or the other of the two plates of a conventional moulding press, it is known to employ clamping devices which must ensure perfectly efficient connection, while being easy and rapid to maneuver in order to facilitate replacement of one mould by another. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a clamping device actuated by compressed fluid which is adapted to respond particularly well to the requirements of the art. 
     The device according to the invention comprises a slide element which is guided along an oblique plane against the inner face of one of the plates of a press and which is actuated by a hydraulic jack of the double-effect type. This slide element has an opening with two diameters, in the form of a button-hole, cut out therein, adapted to cooperate with the projecting head and shank of a catch secured on the corresponding face of the element of the mould. At the level of this catch, the inner face of each plate has a housing hollowed out therein, inside which slides a pusher element associated with an elastic member which enables the pusher element to recoil during clamping of the pieces and, which also drives out the head of the catch during unlocking. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be more readily understood on reading the following description with reference to the accompanying drawings, in which: 
     FIG. 1 is a vertical section showing in superposition, prior to assembly thereof, a press plate and a mould element equipped with a clamping device according to the invention. 
     FIG. 2 is a transverse section showing the guiding of the slide element of the device according to the invention. 
     FIG. 3 is a plan view of the slide element assumed to be in the dismantled state. 
     FIGS. 4 and 5 are longitudinal sections similar to that of FIG. 1, showing the parts of the device at two phases of the operating cycle. 
     FIGS. 6 and 7 are horizontal sections in detail illustrating the relative position of the slide element and of the catch at the phases corresponding to FIG. 4 and to FIG. 5. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, it has been assumed that the clamping device shown is used for securing a mould element 1 against the lower face of the upper plate 2 of any moulding press. 
     The device secured, a catch 3 screwed or otherwise fixed on the element 1 in order to project from the upper face of the element. It will be observed that this catch 3 comprises a cylindrical shank 3a provided with an upper head 3b of larger diameter. 
     Opposite each of the catches 3 provided on the element 1, the plate 2 comprises a cylindrical bushing 4 added in a vertical blind housing in the plate. In the inner housing defined by this bushing 4, there axially slides a pusher element 5 that a spring 6 tends to drive outwardly, the movement of the pusher element is limited by bearing against an annular ring 7 engaged in a groove in the bushing 4. It will be observed that the face of the pusher element 5 which faces downwardly, has an impression 5a of conical profile hollowed out therein, adapted to receive the upper part, itself of truncated section, of the projecting head 3b of the catch 3. 
     There is added against the lower face of the plate 2 a piece 8 (FIG. 2) which forms a slideway for guiding a slide element 9 with reciprocating movement. It will be noted that the longitudinal grooves of the piece or slideway 8 are oriented obliquely, with the result that the slide element 9, connected by an oblique rod 10 to piston 11 (FIG. 1) of a hydraulic jack 11-12 of the double-effect type, moves along a plane which is oriented obliquely with respect to the flat lower face of the plate 2. The cylinder 12 is of course rigidly fixed against the lateral wall of the plate 2. 
     As shown in detail in FIG. 3, the slide element 9 has a vertical opening, in the form of a button-hole, cut out therein, presenting a part 9a whose inner diameter corresponds, to within a slight clearance, to the diameter of the shank 3a of the catch 3, and a part 9b of larger diameter, adapted to be traversed by the projecting head 3b of the catch. 
     Operation of the clampIng device described hereinabove follows from the foregoing explanations and will in any case be described with reference to FIGS. 4 to 7. 
     In FIG. 4, it has been assumed that, with a view to securing the element 1 of the mould against the plate 2 of the press, the element 1 has been positioned so that the catch 3 of each of the clamping devices is disposed in register with the corresponding bushing 4 of this 2. It will be readily appreciated that, by bringing the two pieces 2 and 1 together, the head 3b of each catch 3 is extended through the part 9b having the large diameter opening therein. The slide having been brought to in aligned position by the jack 11-12 being extended to the position shown in FIG. 4. 
     It will be noted that the conical impression 5a of the pusher elements 5 ensures, in connection with the upper part of the projecting head 3b of the catches 3, self-centering of the two pieces 1 and 2. It then suffices to admit the hydraulic fluid into the front chamber of the jack 11-12 (arrow F1 of FIG. 4). As shown in FIG. 5, recoil of the piston 11 provokes the oblique displacement of the slide element 9; the edges of the part 9a of smaller diameter abut against the annular lower face of the head 3b of each catch 3, consequently exerting a vertical effort which ensures clamping of the two pieces 1 and 2. A comparative examination of FIGS. 6 and 7 clearly shows that the cooperation of the slide element 9 and of the projecting head 3b of the catch 3 effects a perfectly efficient locking. 
     It should be observed that, due to the obliqueness of the grooves of the slideway 8 and to the forces of friction thus generated, a self-locking effect is obtained which ensures maintenance of the clamping, even if a breakdown occurred in the hydraulic circuit associated with the jack 11-12 during use of the press. 
     The clamping has of course provoked recoil of the pusher element 5 in the bushing 4, against the spring 6. To effect unlocking of the two pieces 1 and 2, it suffices to admit the fluid under pressure in the rear chamber of the jack 11-12 (arrow F2 of FIG. 5). Since, due to the presence of the rod 10 inside the opposite chamber, the unlocking effort is in any case greater than the clamping force previously developed, there cannot be any locking and the slide element 9 is returned to its position according to FIGS. 4 and 6. The spring 6 thereafter drives the pusher element 5 and the catch 3 downwardly, so that the element 1 is detached from the plate 2 by a distance d which facilitates removal thereof. 
     The whole manoeuvring does not require any manual mechanical intervention. The equipment to be provided on the moulds is inexpensive and comprises no hindrance since each mould element may project with respect to the corresponding plate. 
     However, it goes without saying that, in certain particular cases, the arrangement may be reversed, in that the catches 3 may be provided on each plate of the press, the slide elements 9 and the jacks 11-12 in that case being fixed on the mould elements. 
     It must, moreover, be understood that the foregoing description has been given only by way of example and that it in no way limits the domain of the invention which would not be exceeded by replacing the details of execution described by any other equivalents.