EP0931644A1

EP0931644A1 - Press for pressing tiles made of cement together with any aggregate such as crushed stone or the like

Info

Publication number: EP0931644A1
Application number: EP99830006A
Authority: EP
Inventors: Alfredo Longinotti
Original assignee: Longinotti Meccanica SRL
Current assignee: Longinotti Meccanica SRL
Priority date: 1998-01-21
Filing date: 1999-01-14
Publication date: 1999-07-28
Also published as: ITFI980018A0; ITFI980018A1

Abstract

The press has molds (3) with multiple molding cavities (3A) and respective multiple rams (9) on a movable pressing assembly (7). A variable-volume chamber (8) containing liquid is provided in each ram (9) and the various chambers are interconnected so that pressing occurs with the same pressure in all the molding cavities (3A) by means of the liquid of said chambers.

Description

In the process for manufacturing tiles made of crushed stone and cement, the tiles are formed by pressing in a mold, by means of a respective ram, a certain quantity of a watery mixture of cement and aggregate, such as silica or crushed stone. In order to increase the productivity, the presses commonly used for this operation are generally provided with a multiple mold having a multiplicity of seats and respective rams for obtaining several tiles for each pressing cycle. This arrangement has the disadvantage that inevitable differences in quantity and compactness of the mixture deposited in the various molding cavities produce - on account of the lack of flexibility in the relative positioning of the rams - varying compression of the tiles in the various molding cavities. This drawback is relatively acceptable in the case of tiles which are formed by superimposing a semi-dry layer of sand and a layer of said watery mixture; this is because these tiles, which are pressed at a relatively low pressure, have small differences in compactness and a thickness such that it is possible to compensate for any differences by means of subsequent fine-sizing machining operations.
On the other hand, tiles of the type which have a relatively small thickness (approx. 12-15 mm) are formed by a single layer of watery mixture and require substantially higher pressures. In these conditions, said differences in mixture quantity and compactness result in a considerable quantity of machining rejects.
According to the present invention, in order to eliminate substantially this drawback, a variable-volume chamber containing liquid is provided in each seat and, more preferably, inside the respective ram, and the various chambers are connected to one another by means of a connection ducting. In this way, during pressing, the differences in pressure between the various molding cavities of the mold are eliminated and the tiles, after pressing, have a uniform compactness.
In a preferred embodiment, each of said variable-volume chambers containing liquid consists of a cylinder/piston system, the cylinder of which is formed in the ram itself and, in said movable assembly, ducts establishing communication between the variable-volume chambers formed by said cylinder/piston systems are provided. In this way the movable assembly with the rams is free from pipes which could be damaged during operation.
The invention will be better understood with reference to the description and the attached drawing which shows a non-limiting example of invention itself. In the drawing:
Fig. 1 shows a side view of a movable ram-carrying assembly and a mold for tiles according to the invention, sectioned along an axial plane;
Fig. 2 shows a plan view of a detail of the movable assembly according to Fig. 1, sectioned along a plane indicated by II-II; and
Fig. 3 shows a partial side view of said movable assembly, sectioned along a plane indicated by III-III in Fig. 2.
The press comprises a framework, not shown in the drawing, which has a surface 1A for supporting the mold, i.e. the frame 3 and an upper crosspiece 1B which houses a hydraulic cylinder 5, to the stem 5A of which a movable assembly 7 carrying rams 9 is attached.
The mold 3 rests on the surface 1A via a plate 11 with a resilient laminar element, preferably made of rubber or the like, and has two or more through-seats 3A for forming two or more tiles during each stroke of the press. The seats each have the reverse shape of the tile to be pressed and a height suitable for receiving, with a considerable margin, all the material necessary for obtaining a tile.
The mold, instead of being of the traditional type indicated above, may also be of a type which allows drainage and discharging downward, as illustrated for example in the Italian applications No. FI96A276 dated 27.11.1996 and No. FI97A178 dated 24.7.1997 in the name of the same Proprietor.
The movable assembly 7 has a body 7A which is fixed at the bottom of the stem of the piston 5A of the press and underneath which a ram-carrying plate 7B is fixed. A variable-volume chamber 8 is provided in each ram 9, which has a base 9A with the same plan-view shape as the tile to be pressed such that it can be inserted with a small amount of play inside a respective facing seat 3A, and a cylindrical cavity 9B with an axis Z-Z, by means of which the ram itself is mounted with a minimum amount of play onto a respective piston 13 via seals 14. Each piston 13 has at the top a stem with a small cross section and is fixed undemeath the plate 7B of the movable assembly 7 by means of screws or another fixing system not shown. A shaped plate 9C is fixed at the top of each ram 9 and projects inward toward the stem of the piston 13 so as to act as a downward end-of-travel stop for the ram 9 with respect to the piston 13. Each variable-volume chamber 8 is defined by the cavity 9B of the piston 13.
In order to provide each ram 9 with the same angular orientation about said axis Z-Z of the corresponding seat 3A of the mold, each ram 9 has a pin 15 (see also Figs. 2, 3) which is fixed to the plate 7B by means of a threaded shank of the pin itself, passing into a hole of the plate 7B and a nut. Said pin penetrates slidably inside a hole of the ram 9 so that a relative movement of the ram 9 and the plate 7B along the axis Z-Z, but not an angular movement of the ram 9 about said axis Z-Z, is permitted.
Each piston 13 has, passing through it, a hole 13A which hydraulically connects the chamber 8 (defined between the piston 13 itself and the ram 9) to a ducting 7C which extends inside the plate 7B. The ducting 7C therefore connects together said chambers 8 of all the rams 9 and leads into an end element 17 which comprises a pressure gauge 17A and a breather hole 17B closed by a stopper. The end element 17 also comprises a non-return valve 17C arranged between the ducting itself and an oil filling opening 17D, said opening being normally closed by a respective stopper. A flexible seal 19 is arranged outside each ram 9 and the plate 7B so as to prevent the deposition of dust or crushed stone between the ram itself and the corresponding piston 13.
During operation, each seat 3A receives internally a quantity of cement mixed with crushed stone and any aggregate sufficient for forming a tile. The cement mixture is deposited in each seat 3A in a quantity which depends on the final thickness of the tile, the percentage of water contained in the mixture and the composition and grain size of the mixture itself. Since the mixture has been removed from different points of a mass which, for practical reasons, is not perfectly homogeneous, said quantities may be different and result in thicknesses S1, S2 of the mixture which are different from one another inside the various seats, i.e. molding cavities 3A. For this reason, variable-volume chambers 8 communicating with one another are provided. Before starting the processes for pressing the tiles, hydraulic oil is injected through the opening 17D into the ducting 7C until the oil chambers 8 are filled, with bleeding of the air already contained therein through the breather hole 17B.
The quantity of oil injected is such that, with the faces 9A of the rams coplanar, the chambers 8 have a greater height (for example of at least 2 mm) than the maximum foreseeable difference in thickness S2-S1. In this way, when the piston 5A is lowered in order to perform pressing, the first ram 9 which encounters the material to be pressed (the right-hand ram in Fig. 1) transfers oil from its chamber 8 to the chamber of the other ram or rams, causing a further downward movement of the latter until they are all brought into contact with the material deposited in the corresponding seats. A uniform pressure is therefore established inside the chambers 8, said pressure corresponding to uniform pressing of the tiles being formed inside the various seats 3A of the mold 3, independently of the abovementioned differences in thickness.
With the subsequent fine-sizing machining operations, in particular using diamond-coated disks, the thicknesses of the tiles produced are easily rendered uniform.
It is understood that the drawing shows only one example of embodiment provided merely by way of a practical demonstration of the invention, whereby the forms and arrangements of said invention may vary without thereby departing from the scope of the idea underlying the invention itself. The presence of any reference numbers in the accompanying claims has the object of facilitating reading of the claims with reference to the description and does not limit the scope of protection represented by the claims.

Claims

Press for pressing tiles made of cement together with any aggregate (crushed stone or the like), comprising molds (3) with multiple molding cavities, i.e. seats (3A), also of the draining type, and respective multiple rams (9) on the movable pressing assembly (7), characterized in that a variable-volume chamber (8) containing liquid is provided in the region of each molding cavity (3A) and/or the respective ram (9), the various chambers being interconnected so that pressing occurs with the same pressure in all the molding cavities (3A) by means of the liquid of said chambers.
Press for pressing tiles made of cement together with any aggregate (crushed stone or the like), comprising molds (3) with multiple molding cavities, i.e. seats, and respective multiple rams (9) on the movable pressing assembly, characterized in that each ram (9) has a variable-volume chamber (8) containing liquid, the various chambers (8) being interconnected so that pressing occurs with the same pressure in all the molding cavities (3A) by means of the liquid of said chambers.
Press as claimed in claim 2, characterized in that the movable pressing assembly (7) forms the pistons (13) of cylinder/piston systems, the cylinders (9B) of which are formed in the multiple rams (9) and in that ducts (13A, 7C) forming an interconnection between the variable-volume chambers (8) consisting of said cylinder/piston systems are provided in said movable assembly (7).
Press as claimed in claim 3, characterized in that, for each ram (9), in addition to said cylinder/piston system, the movable pressing assembly (7) has a guide (15) parallel to the axis (Z-Z) of said piston-cylinder for defining the angular position of the ram (9) with respect to the movable assembly (7) itself and the respective seat (3A).
Press as claimed in claim 4, characterized in that said guide comprises a pin (15) fixed to said movable assembly and projecting from the bottom thereof so as to penetrate with a slight amount of play inside a hole of the ram (9).
Press as claimed in at least one of the preceding claims, characterized in that each said cylinder/piston system has an extra amount of travel with respect to the maximum relative expected error (S2-S1) in the thickness of the pressed tiles.
Press as claimed in claim 6, characterized in that said extra travel is of the order of at least 2 mm.
Press as claimed in at least one of claims 2 and the following claims, characterized in that it comprises a flexible seal (19) between each ram (9) and the movable assembly (7) which carries the respective pistons.
Press for pressing tiles made of cement together with any aggregate such as crushed stone or the like, all of which as described and illustrated by way of example in the accompanying drawing.