Deformable support for use during foaming, and method of making such a support

Abstract: A plunger (10) for supporting a wall (46) of e.g. a refrigerator door on filling of expanding an hardening foamed plastic (52) on the other side of the wall shows an evacuated bag-formed part (18) filled with a particulate material (20), which part has a surface (42) showing an impression of the form of the wall (46). The plunger (10) is reshapable, so that it can serve as a plunger for walls (46) of different forms.

Description: The invention refers to a method of supporting one side of a wall by using a plunger, as the space behind the other side of the wall is filled with expanding and hardening plastic foam. On making a common type of refrigerator doors showing an outer wall of sheet metal and an inner wall of plastic, the walls are placed in a fixture, the space between the walls thereafter being filled with expanding and hardening plastics foam. The purpose of the fixture is to support the walls against the overpressure exerted by the foam before it has hardened and thereby prevent the walls from changing form. It is particularly important that the fixture supports all parts of the inner wall which is relatively weak by itself and often shows a very irregular form. For this purpose, this part of the fixture is constituted by a detachable plunger which is accurately formed after the inner wall, so that it shows a substantially complete impression of the inner wall, the plunger supporting the wall by said impression. It can take 8 minutes for the foam to harden in the space between the walls. On multiple production of one refrigerator per minute, 8 fixtures with 8 identical plungers therefore might be needed. A manufacturer of refrigerator doors can make door types showing inner walls of e.g. 60 different forms. This requires 8 x 60 = 480 plungers. It is known to make such plungers of wood or metal having the drawback to be very expensive. An other drawback with the large number of plungers is that they take valuable place in the factory. The object of the invention is to achieve a method of supporting one side of a wall by using a plunger of the kind introductorily set forth which requires a small labour effort and allows the plunger to be easily reshaped, so that it can be used as a plunger for walls of different forms, the number of plungers being necessary for a production thereby becoming substantially reduced. This object is obtained by the method according to the invention thereby that the plunger comprises a rigid plate and a flexible, bag-like part which is filled with particulate material, whereby the bag-like part of the plunger is pressed against a mould which has a shape corresponding to that of the wall, evacuating the bag-like part to produce a stable impression of the wall in the particulate material, injecting plastic foam into the space behind the wall, the wall thus being supported by application of the plunger. An embodiment of the invention is described below in connection with the enclosed drawing, on which Fig. 1 in a sectional view shows a plunger before it has been formed, Fig. 2 shows a mould for forming the plunger, Fig. 3 shows how the plunger has been formed after the mould, Fig. 4 shows the plunger after the forming, Fig. 5 shows a refrigerator door prepared to be filled with plastics foam and Fig. 6 shows the plunger supporting a wall of the door when the door has been filled with expanding and hardening foamed plastic. By 10, see Fig. 1, is designated a plunger comprising a rigid plate 12 having an opening 14 which is coverable by a lid 16. A flexible bag-formed part 18 of plastic film is fastened to the plate 12. Through the opening 14 the part 18 has been filled with a particulate material 20 in the shape of small plastic balls. A conduit 22 with a cut-off valve 24 is arranged in the lid 16. After the opening 14 has been covered by the lid 16, the air in the space 26 of the bag-formed part 18 is evacuatable through the conduit 22. By 30, see Fig. 2, is designated a mould showing the form of an inner wall of a refrigerator door. The surface 32 of the mould shows ducts 34 communicating with a space 36, which is evacuatable by a conduit 38. The plunger 10 is placed, see Fig. 3, with the bag-formed part 18 against the mould 30. Air is sucked out through the conduit 38, so that the part 18 is sucked against the surface 32 and takes its form. After that, the plunger 10 with the part 18 is pressed against the mould 30 by an outer force 40, so that the plastic balls cannot move relative to each other, simultaneously as the air in the space 26 is evacuated through the conduit 22. In this way the plunger is made, which is shown in Fig. 4, where the bag-formed part 18 now constitutes a rigid body showing a precise impression 42 of the surface 32 of the mould 30. The vacuum in the space 26 is kept by the valve 24 being closed. In Fig. 5 is shown a refrigerator door constituted by an outer plane prefabricated wall 44 of sheet metal and an inner prefabricated wall 46 of thin rigid plastic. The walls 44 and 46 are kept fixed relative to each other in a fixture 48. In Fig. 6, the plunger has been laid on the wall 46, so that the form of the wall 46 fits in the corresponding form of the plunger. The fixture 48 and the plunger 10 are kept together, so that they cannot move from each other. After that, the space 50 between the walls 44 and 46 is filled with expanding and hardening foamed plastic 52, the plunger 10 supporting against the wall 46 and preventing it from being deformed during the time the foam hardens. By letting air into the space 26, the plunger 10 can be made to retake the form shown in Fig. 1. The plunger can then be reshaped to match the walls 46 whatever form they take and can then serve as a plunger for these.

Claims: A method of supporting one side of a wall (46) by using a plunger, as the space (50) behind the other side of the wall is filled with expanding and hardening plastic foam (52), characterized in that the plunger comprises a rigid plate (12) and a flexible, bag-like part (18) which is filled with particulate material (20), whereby the bag-like part of the plunger is pressed against a mould (30) which has a shape corresponding to that of the wall (46), evacuating the bag-like part (18) to produce a stable impression of the wall (46) in the particulate material (20), injecting plastic foam into the space (50) behind the wall (46), the wall (46) thus being supported by application of the plunger. Method according to claim 1, characterized in that before the evacuating of the bag-like part (18) the space between the bag-like part (18) and the mould (30) is evacuated, so that the bag-like part is sucked against the mould.

Inventors: STALIN ANN CHARLOTTE NIKITA, STALIN, ANN CHARLOTTE NIKITA
Applicants: ELECTROLUX AB, AKTIEBOLAGET ELECTROLUX
Application year: 1990
Main classification: B29C44
IPC codes: B29C33, B29C44