PRESS FOR FOAMING INSULATING PANELS

Abstract: The invention consists of a press for foaming insulating panels, which has a movable upper plate (2) and fixed lower plate (3) between which a panel to be foamed (9) is inserted. A frame (1) integrally constrained to the movable upper plate (2) and brought into abutment against the fixed lower plate (3) results in the formation of a chamber (8) containing the panel to be foamed (9), inside which it is possible to produce the vacuum by means of the action of an upper seal (5a) and a lower seal (5b).

Description: PRESS FOR FOAMING INSULATING PANELS Description The present invention relates to a press for foaming insulating panels. The use of panels consisting of two containment sheets and an inner layer of insulating material has for some time been adopted in a wide range of sectors: one need only consider the need for insulating, both thermally and acoustically, living and working environments, as well as the need for thermally insulating environments including those of a transportable nature - intended for storing food products or in any case requiring a constant ambient temperature. The foaming of insulating panels is obtained by means of the injection of a polyurethane compound into the space existing between two containment sheets and associated connecting end-sections: this polyurethane compound, once injected, expands, giving rise to a reaction producing on the two containment sheets a pressure of 0.4 to 0.7 kg/cm 2 . For this reason, the known technology for the production of these foamed panels makes use of machines, called presses, in which the external surfaces of both the containment sheets are positioned in contact with two steel plates which have the function of opposing deformation of the sheets themselves due to the action of internal expansion of the polyurethane compound. It must be noted that, on some occasions, the contact between containment sheets of the panels and plates of the press is cushioned by layers usually of formica, designed to dissipate the heat which forms during the process involving expansion of the polyurethane compound. During the reaction which occurs in the injected polyurethane compound, air bubbles are formed, these air bubbles remaining trapped in the mass of the insulating layer, once the reaction has been completed. These air bubbles are undesirable since they generate discontinuity in the polyurethane mass with a corresponding lack of uniformity in the insulating power of the mass itself. These bubbles moreover reduce the mechanical strength of the panel itself, rendering the latter sometimes unacceptable or resulting in the need for over- dimensioning, especially in the case of motor-transported refrigerating units. In order to reduce the excessively large dimensions of the panels, in many cases use is made of additives which increase the expansion pressure up to as much as 2 kg/m 2 , but this results in a notable overdimensioning of the structure of the press with considerable plant and operating costs. Another drawback present in the known technology for the production of said insulating panels is due to the fact that, during the reaction of the polyurethane resin, inflammable and toxic gases are released and at present discharged into the atmosphere. One object of the present invention is that of providing a press for foaming insulating panels, provided with a system designed to avoid the trapping of air bubbles in the polyurethane compound injected within the containment sheets of the panels themselves. Another object of the present invention, which is a direct consequence of the first one, is obtaining a reduction in the pressure exerted on the press plates by the containment sheets of the panels during foaming with the advantage of being able to provide a press with a lightened support structure. These and other objects are all achieved by the press for foaming insulating panels according to the present invention, of the type comprising two plates which can be arranged above one another and one of which is movable with respect to the other one which is fixed, characterized in that one of the two plates carries, integrally constrained thereto, a frame of height equal to the thickness of the panel to be foamed and with a perimetral extension greater than that of the aforementioned panel, said frame with the two plates forming a chamber connected to a pneumatic plant designed to produce the vacuum in said chamber. These and other characteristic features will emerge more clearly from the following description of a preferred embodiment illustrated, purely by way of a non-limiting example, in the accompanying drawings, in which: - Figure 1) shows a partial side view of a portion of the press according to the present invention; - Figure 2) shows a diagrammatic partial plan view of the same portion of the press. The figures show partially a press for foaming insulating panels comprising a movable upper plate 2 which carries, integrally constrained thereto, a frame 1 of height equal to the thickness of a panel to be foamed 9 and with a perimetral extension greater than that of the said panel; the frame 1 has over its entire outer perimeter a plate 4 constrained to the aforementioned frame by the tightening of bolts and this tightening action enables an upper seal 5a and a lower seal 5b to be retained between the plate 4 and frame 1. A fixed lower plate 3 of the press has passing through it, via a duct 6, a pipe of a vacuum-generating plant provided with a filter 7. The movable upper plate 2 is moved by four helical-screw, square-profile, mechanical jacks 11 which are connected together by a kinematic chain so as to ensure the absolute synchronism of movement of the aforementioned mechanical jacks 11 and consequently the totally regular operation of the movable upper plate 2. The operating principle of the press according to the present invention is now described in connection with the reference numbers shown in the Figures. Once the panel to be foamed 9 has been positioned on the formica layer 14b fixed to the upper side of the of the lower plate 3 of the press, the four mechanical jacks 11 start up simultaneously and cause lowering of the movable upper plate 2 of the press. Each screw of each mechanical jack 11, which is translated axially and vertically, has at its top end a polygonal flange 15 which is inserted into a special seat 15a formed in the thickness of the movable upper plate 2; this seat 15a has the function of centring each flange 15 and prevents any lateral displacement of the aforementioned upper plate, but allows the upper plate to be raised freely if the pressure of the polyurethane mass increases beyond the preset value owing, for example, to the greater quantity of foam injected. As a result, the screws of the four mechanical jacks 11 are able to perform the function both of moving the movable upper plate 2 and of ensuring perfect vertical guiding thereof without creating any reactive forces on the press structure. These jacks could also be more than four in number if the upper plate of the press should have particularly large plan dimensions. The aforementioned movable upper plate carries on its bottom side, in addition to the formica layer 14a, the frame 1, the associated perimetral plate 4 and the two seals, i.e. upper seal 5a and lower seal 5b; the upper seal 5a has already been compressed, during assembly of the press, against the movable upper plate 2. The lowering movement of the movable upper plate 2 continues until the frame 1 strikes against the upper side of the fixed lower plate 3; when this contact occurs the lower seal 5b is compressed against the fixed lower plate 3. At this point the panel to be foamed 9 is not only perfectly locked in position between the two formica layers 14a and 14b, but is also situated inside a chamber 8 which is sealed with respect to the surrounding environment by the seals 5a and 5b. The next stage is that of obtaining the vacuum inside the chamber 8 by means of a plant suitable for this purpose, of a known type and not illustrated, the piping of which passing through the fixed lower plate 3 of the press via the duct 6 terminates inside the aforementioned chamber 8 with the filter 7. The vacuum generated inside the chamber 8 prevents the formation of air bubbles inside the polyurethane mass 12 during the expansion process thereof because there is no sealing between the containment sheets 10a and 10b of the panel 9, between the latter and the plates 2 and 3 of the press and the formica layers 14a and 14b, nor between the polyurethane mass 12 and the connecting end-sections 13. The air extracted from the chamber 8 also contains toxic gases due to the chemical reaction and therefore may be advantageously conveyed into suitable filtering plants. In the description provided above specific reference has been made to a press with a vertically movable upper plate and a fixed lower plate, but it is obvious that other configurations may also be adopted both as regards the moving plate and as regards the nature of this movement, for example of the folding type. As regards movement of the movable plate, it is also possible to adopt solutions other than the mechanical jacks illustrated in the above description, such as for example hydraulic systems or the like, suitable in any case for ensuring absolute synchronism between all the moving groups of the movable plate. The press may also consist of several surfaces or levels located above one another, each level being provided with a frame for creating a chamber connected to the vacuum plant .

Claims: Claims 1. Press for foaming insulating panels of the type comprising two plates which can be arranged above one another and one of which is movable with respect to the other one which is fixed, characterized in that one of the two plates carries, integrally constrained thereto, a frame (1) of height equal to the thickness of the panel to be foamed and with a perimetral extension greater than that of the aforementioned panel, said frame with the two plates forming a chamber connected to a pneumatic plant designed to produce the vacuum in said chamber. 2. Press according to Claim 1, characterized in that the frame (1) has over its entire outer perimeter a plate (4) constrained to the aforementioned frame by means of the tightening of bolts, said tightening enabling an upper seal (5a) and a lower seal (5b) to be retained between the plate (4) and frame (1). 3. Press according to Claim 1, characterized in that it has a movable upper plate (2), a frame (1) integral with said movable plate and a fixed lower plate (3) . 4. Press for foaming insulating panels, characterized in that it comprises four mechanical jacks (11) for vertical movement of the movable upper plate (2), the screw of each of which jacks has at its top end a flange (15) which is inserted into a special seat (15a) formed in the thickness of the movable upper plate (2), this seat having the function of centring each flange (15) and preventing any lateral displacement of the movable upper plate (2) and maintaining the freedom for vertical axial displacements of said upper plate.

Inventors: ADAMI FEDERICO, ADAMI, FEDERICO
Applicants: ADAMI FEDERICO, ADAMI, FEDERICO
Application year: 1996
Main classification: B29C44
IPC codes: B29C33, B29C44