VERTICAL PRESS FOR THE MOULDING OF PLASTICS MATERIALS, PARTICULARLY THERMOSETTING PLASTICS MATERIALS

Abstract: A vertical press for the moulding of plastics mate­ rials, particularly thermosetting plastics materials, comprises a fixed plate (4) and a movable plate (8) slidable on guide colums (6), first fluid-operated actuator means (10) for moving the movable plate along the guide columns,fluid-operated clamping means (12) associated with the movable plate for clamping the movable plate relative to the guide columns, and second fluid-operated actuator means (36) acting on the guide columns to move the columns vertically relative to the fixed plate.

Description: The present invention relates to a vertical press for the moulding of plastics materials, particularly thermosetting plastics materials. Vertical presses for thermosetting plastics materials are known which are provided with a fixed plate and a movable plate having large cylinders which move the movable plate towards the fixed plate. Due to the large dimensions of the actuator cylinders, the movement of the movable plate in these presses involves movements of large quantities of oil. Vertical presses are also known which are provided with mechanical means for clamping the movable plate and with actuator means which cause upward vertical movement of the other plate. This system involves great complications, particularly when an injection unit it installed, since it is necessary also to move the injection unit during the injection-compression process. More particularly the present invention relates to a vertical press having the features disclosed in the precharacterising portion of claim 1. EP-A-0 220 634 discloses a press of this kind for molding polyurethan articles, wherein in the annular recesses of the movable plate annular partition elements are movably mounted around the columns and are provided with fluidic means, which can clamp them to the columns, so that separate upper and lower annular chambers are formed in each recess. In the operation of this latter press the first actuator means provide for a first stage of movement of the movable plate towards the fixed plate. Then the annular partition elements are clamped to the columns and pressurised oil is introduced in the lower chambers of the recess, so that the movable plate is further pushed towards the fixed plate with the desired force and the molding can be effected. Afterwards the movable plate is removed from the fixed plate in a two stages movement, introducing at first pressurised oil in the upper chambers of the recesses and then, after having unclamped the partition elements from the columns, operating the first actuator means. The object of the present invention is to produce a press which enables high-speed operation with reduced quantities of oil and whose height is limited. This object is achieved by virtue of a vertical press having the features further disclosed in the characterising portion of claim 1. Further characteristics and advantages of the press according to the invention will become clear from the detailed description which follows with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure 1 is a partially-sectioned front elevational view of a vertical press according to the invention, Figure 2 is a section of a detail of Figure 1 on an enlarged scale. With reference to the drawings, a vertical press comprises a support structure 2 on which a fixed plate 4 is mounted. Four guide columns 6 on which a movable plate 8 is slidably mounted extend from the support structure, perpendicular to the fixed plate. The plate 8 is operated by means of an oleodynamic actuator 10 which moves this plate along the guide columns. Four clamping devices, generally indicated 12, are associated with the movable plate and each acts on a respective guide column 6. Each clamping device, illustrated in greater detail in Figure 2, comprises a bush-like element 14 of annular section formed by 2 adjacent annular half-elements 14a and 14b which surround the respective guide column 6 and are housed in a respective cylindrical chamber in the plate 8. Oil is supplied under pressure to the cylindrical chamber through a tubular connector 17 and causes elastic deformation of the steel annular half-elements 14a and 14b, thus clamping the movable plate to the guide column. The chamber 16 is sealed by means of sealing rings 20. In the embodiment illustrated in Figure 2, each annular half-element 14a and 14b includes a circular cylindrical portion with a friction surface 22 and a frusto-conical end portion 24. Sealing rings 26 and 28 are interposed between each annular half-element and the guide column and the wall of the cylindrical chamber 16, respectively. The pressurised oil is supplied through the duct 17 into an annular chamber 30 defined between the element 14 and the wall of the cylindrical chamber and from there, through a passage 32 between the two half-elements, into a second annular chamber 34 defined between the 2 half-elements and the guide column. The sealing rings 26 prevent the pressurised oil from infiltrating and coming into contact with the friction surface 22. Second actuator means, generally indicated 36, are associated with the guide columns 6 for moving them relative to the fixed plate 4. For this purpose, the lower end of each column acts as a double-acting piston 38 within a cylindrical chamber 40 formed in the support element 2. The operation of the press according to the invention provides for a first stage of movement of the movable plate towards the fixed plate at high speed by means of the operation of the oleodynamic cylinder 10. During this stage, high oil pressures are not required and the oleodynamic cylinder may be of small section. The movable plate is then clamped at a prescribed distance from the fixed plate by means of the operation of the clamping means 12, after which begins the stage of downward movement of the movable plate at high pressure, by means of the actuators 36 acting on the columns. The system for clamping the movable plate to the columns enables movement at high pressure to be achieved with a small quantity of oil. Furthermore, it is possible to supply the pressurised oil to the clamping means 12 and to the actuators 36 by means of a single source of pressurised oil

Claims: A vertical press for the moulding of plastics materials, comprising: a support structure (2), a fixed plate (4) supported by said structure (2), guide columns (6) mounted on said support structure (4) and a movable plate (8) slidably mounted on said guide columns (6) and comprising annular recesses (16) surrounding each of said columns (6); and first fluid-operated actuator means (10) connected between said columns (6) and said movable plate (8) for moving said movable plate (8) along the guide columns (6); characterised in that it comprises: second fluid-operated actuator means (36) on said fixed plate (4) acting on said guide columns (6) to move said guide columns (6) vertically relative to said fixed plate (4); and a plurality of fluid-operated clamping means (12) carried by said movable plate (8) for clamping said movable plate (8) against relative movement with respect to each guide column (6), each of said fluid-operated clamping means (12) comprising a pair of annular steel bushing elements (14) located in said recess (16) in spaced relation to each other to define an annular pressure chamber (30) therebetween, fluid passage means (17) extending through said movable plate (8) into communication with said pressure chamber (30) for supplying pressurized fluid to said chamber (30), each of said bushing elements (14) having a first portion disposed in sliding engagement with said recess and said column (6), sealing means (26, 28) between said first portion and said movable plate (8) and said column (6) respectively, a second portion spaced from said recess and having a circular cylindrical friction surface (22) disposed in engagement with said column (6), and a frusto-conical part (24) spaced from a bottom wall of said recess (16) and said column (6) and extending between said second portion and an end wall of said recess (16), whereby upon introduction of pressurized fluid into said pressure chamber each of said annular bushing (14) will undergo elastic deformation to clamp said movable plate (8) to said guide column (6).

Inventors: CHIESI, FRANCO
Applicants: FIAT AUTO S.P.A.
Application year: 1988
Main classification: B29C45
IPC codes: B29C45