Closing unit for the die in double-toggle machines for the molding of plastic materials or for die casting

Abstract: This invention relates to a closing unit for the die in double-toggle machines for the molding of plastic materials or for die casting having a base (11), four horizontal columns (12) which pass in a stationary die-holder plate (13) attached on the base, in a movable die-holder plate guided on the base and along the said columns, and in a closing plate (15) positionable on the base, the movable die-holder plate (14) and the closing plate (15) being connected by means of toggle mechanisms (18). A movable control part (20) in the form of a ring is placed on the base between the movable die-holder plate (14) and the closing plate (15),sliding on the said horizontal columns and connected by means of connecting rods (18c) to the toggle mechanisms (18).

Description: The present invention relates to a closing unit for the die in double-toggle machines for the molding of plastic materials or for die casting according to the precharacterising portion of claim 1. Machines for injection molding or for die casting usually comprise a base, four horizontal columns placed above the base according to the vertices of a quadrilateral and passing in a stationary die-bolder plate, attached on the base and resting against blocks applied to one end of the columns, in a movable die-holder plate guided on the base and led along the horizontal columns towards and away from the attached die-holder plate, and in a closing or reaction plate positionable on the base and resting against reaction blocks applied to the other end of the columns. In such machines thus structured, the shifts of locking/unlocking in closing the movable die-holder plate against the stationary die-holder plate are realized by means of a common, so-called double-toggle device, using those of the rods and hinged connecting rods which are extended and withdrawn when operated by at least one hydraulic cylinder. According to a known design, the toggles are normally withdrawn towards the axis of the machine, are connected to a movable crosshead plate, and this is led on a pair of additional guide columns placed in parallel between the horizontal columns of the machine. However, it is evident that the presence of a crosshead plate and of additional columns for guiding it complicate the structure of the machine, obstruct a convenient access to the inside of the structure for maintenance or anything else, and have a negative influence on its production costs. The object of the present invention is to eliminate these disadvantages and to provide a machine for injection molding or for die casting which has a very simple and open structure, is very easy to access and is very economical. In fact, the principal purpose of the present invention is that of providing a machine in which the movable element, to which the toggles are connected, is guided on the machine's own horizontal columns, thus eliminating the additional guide columns present in the known toggle machines. Another purpose of the invention is to provide a machine of the above-mentioned type in which the toggles at the opening of the machine are withdrawn towards the outside, the movable part to which they are connected may be guided on horizontal columns directly or through interposed elements, and control cylinders may be applied to the movable part or to the reaction plate of the machine. The above object is attained according to the invention by a closing unit for the die in double-toggle machines for the molding of plastic materials or for die casting as defined in claim 1. Further embodiments of the invention are described in the dependent claims. In any case, the exemplified embodiments of the invention will be made more evident by the description below with reference to the attached drawings in which: Figure 1 shows a machine in the closing position and in which the movable part is led directly on horizontal columns, and the hydraulic cylinders are on the edge of said part; Figure 2 shows a view similar to that in Figure 1, but in the opening position; Figure 3 shows a cross section according to the arrows III-III in Figure 1; Figure 4 shows a machine in the closing position as that in Figure 1, but in which the movable part is led on the horizontal columns indirectly; Figure 5 shows a view of the machine in Figure 4, but in the opening position; Figure 6 shows a machine as in Figure 1 in the opening position, but with toggles placed between the movable part and the movable die-holder plate and control cylinders mounted on the reaction plate; Figure 7 shows a view of the machine in Figure 6, but in the opening position; Figure 8 shows a cross section according to the arrows VIII-VIII in Figure 6; Figure 9 shows a machine in the closing position as that in Figure 6, but with the movable part led on the horizontal columns indirectly; and Figure 10 shows a view of the machine in Figure 9, but in the opening position. In the known manner, a machine for molding plastic materials or for die casting comprises a base 11 above which are horizontally extended four columns 12 displaced according to the vertices of a quadrilateral and passing in a stationary die-holder plate 13, in a movable die-holder plate 14 and in a closing or reaction plate 15, spaced apart in parallel. The stationary die-holder plate 13 is attached on the base and rests against blocks 16 applied to the adjacent end of the columns 12. The movable die-holder plate 14 is shiftable on the base and along the columns 12 towards and away from the stationary plate for the closing/opening of the die. The closing plate 15 is positionable on the base and rests against reaction blocks 17 applied to the other end of the columns 12. For the shifts of closing/opening of the movable die-holder plate 14 are provided toggle mechanisms 18 controlled by at least one hydraulic cylinder 19 by means of a movable part 20 to which the toggles 18 are connected. Very precisely and in accordance with the present invention, the movable part is essentially in the form of a control ring 20-- Figures 1 and 6 -- placed and shiftable in parallel between the movable die-holder plate 14 and the closing plate 15 and crossed by the four horizontal columns 12 of the machine. In the machine example shown in Figures 1,2 and 3, the control ring 20 is guided and directly shiftable along the columns 12, and each toggle 18, on the one hand, is hinged, in 18a, to the movable die-holder plate 14, and on the other hand, is hinged, in 18b, to the closing or reaction plate 15, and in the intermediate part, is connected to the control ring 20 by means of a connecting rod 18c. The control hydraulic cylinders 19 are attached to two opposite sides of said ring 20, and their shafts 19a are connected to the movable die-holder plate 14. The machine shown in Figures 4 and 15 is completely identical to that shown in Figures 1-3, with the only difference that the control ring 20 is not guided directly on the columns 12, but on sliding sleeves 21 fixed, and therefore movable, with the movable die-holder plate 14 and extending part of the length of the columns 12 towards the closing plate 15. In both embodiments, the action of the hydraulic cylinders 19 determines a shift either in closing or in opening the movable die-holder plate, and likewise, the shifts are also limited by the control ring 20 for extending the toggle mechanisms 18 for locking in the closing position and withdrawing them in the opening position. In particular, in opening, the control ring recedes somewhat; the toggles 18, moved by the connecting rod 18c, withdraw, turning towards the outside of the machine from the side of the movable plate 14, between this and the closing plate; the movable plate 14 approaches the control ring 20-- Figures 2 and 5. In practice, the stroke of the control ring 20 along the columns 12 or their sliding sleeves 21 is somewhat brief with respect to that of the movable die-holder plate 14 by closing and opening, the control hydraulic cylinders being on the edge of said ring. In the machine example shown in Figures 6, 7 and 8, the control ring 20 is guided directly along the columns 12 as in Figure 1, but unlike this one, the control hydraulic cylinders 19 are attached to the closing or reaction plate with their shaft 19a connected to said ring, while the toggle mechanisms, in opening, withdraw, turning towards the outside of the machine from the side of said closing plate and in the circle comprised between the ring 20 and the movable die-holder plate. The machine shown in Figures 9 and 10 is completely identical to that shown in Figures 6-8, with the only difference that the control ring 20 is guided on sliding sleeves 22 attached to the closing or reaction plate 15 and extending part of the length of the columns 12 towards the movable die-holder plate 14. In this embodiment with the toggles in reversed position with respect to the executions in Figures 1-5 in the opening and closing phases, the control ring has a very extended stroke, the cylinders always remain attached to the closing plate, and the movable die-holder plate never strictly approaches said ring given the inter-position of the toggles.

Claims: Closing unit for the die in double-toggle machines for the molding of plastic materials or for die casting having a base (11), four horizontal columns (12), placed above the base (11) according to the vertices of a quadrilateral, and passing in a stationary die-holder plate (13) attached on the base (11) and resting against blocks on one end of the columns (12), in a movable die-holder plate (14) guided on the base (11) and along the said columns (12), and in a closing plate (15) positionable on the base (11) and resting against reaction blocks on the other end of the columns (12), the movable die-holder plate (14) and the closing plate (15) being connected by means of toggle mechanisms (18), characterized in that it comprises a movable control part (20) placed on the base (11) between the movable die-holder plate (14) and the closing plate (15), sliding on the said horizontal columns (12) and connected by means of connecting rods (18c) to the said toggle mechanisms (18), and in that said control part (20) is engaged by at least one control hydraulic cylinder (19) for shifting and locking/unlocking in closing the movable die-holder plate (14) against the stationary plate (13). Closing unit according to claim 1, in which said control part (20) is in the form of a ring. Closing unit according to claim 1, in which said control part (20) slides directly on the horizontal columns (12) of the machine. Closing unit according to claim 3, in which the control hydraulic cylinders (19) are attached to the control part (20) and are connected with their shafts (19a) to the movable die-holder plate (14). Closing unit according to claim 1 or 2 in which said control part (20) is led on sliding sleeves (21) fixed and movable with the movable die- holder plate (14) and extending on part of the columns (12) towards the closing plate (15). Closing unit according to claim 5, in which the control hydraulic cylinders (19) are attached to the control part (20) and are connected with their shafts (19a) to the movable die-holder plate (14). Closing unit according to claim 4 or 6, in which the toggle mechanisms (18) at the opening of the movable die-holder plate (14) turn towards the outside of the machine on the part of the said movable die-holder plate (14). Closing unit according to any claim 1 to 3, in which the control hydraulic cylinders (19) are attached to the closing plate (15) and are connected with their shafts (19a) to the control part (20). Closing unit according to claim 1, in which said control part (20) is led on sliding sleeves (22) attached to the closing plate (15) and containing part of the length of the columns (12) towards the movable die-holder plate (14). Closing unit according to claim 9, in which the control hydraulic cylinders (19) are attached to the closing plate (15) and are connected with their shafts (19a) to the control part (20). Closing unit according to claim 9 or 10, in which the toggle mechanisms (18) at the opening of the movable die-holder plate (14) turn towards the outside of the machine on the part of the closing plate (15).

Inventors: BUGATTI EGIDIO, BUGATTI, EGIDIO
Applicants: BMB SPA, B.M.B. S.P.A.
Application year: 1992
Main classification: B29C45
IPC codes: B22D17, B29C45, B29C33