WO1992002360A1 - Hydraulic press with arrangements for moulding long objects - Google Patents

Abstract

Hydraulic press with retaining platen (C) for lower mould (D) secured to the lower part of a hydraulic cylinder (B), with a platen (F) for securing upper mould (E), which is attached to ram-rod (G) in a pivotable manner. Mould (D) is kept closed by the back pressure and opened by the main pressure, which pulls the product along out of lower part (D) of the mould.

Description

Hydraulic press with arrangements for moulding long objects

The present invention relates to a special hydraulic press for manufacturing long pipes, plates, sections etc. consisting preferably of foam plastic. To the plastic material is added an expanding agent which produces a product with closed cells when it is processed in moulds subject to very high pressure.

Using known equipment, it has in the past been only possible to produce short objects. The moulds were then filled with the material and υlaced within traditional hydraulic presses with two or several columns/stays.

After processing the moulds were transferred to other traditional hydraulic presses, where the product was ejected from the moulds by means of a door or similar device.

This process was slow and highly labour-intensive. In addition, problems arose in connection with the ejection of the product from the moulds.

What happened was that at high pressure the product was compressed to a higher degree and adhered even more firmly to the walls of the mould.

With long products the back pressure became so large that the material was crushed.

With the present invention said problems have been resolved. It has become possible to produce objects of several metres length with material densities down to less than 0.2. The invention comprises a quite special columnless hydraulic press, in which one mould-half is secured to a platen/shoulder on the lower half of the hydraulic cylinder. An extended ram-rod bears a cross-head, to which the other half of the tool is secured. The back pressure in the hydraulic cylinder closes the moulds and keeps them closed during the (decomposing) moulding process, subject to very high pressure. The plastic material exhibits high adhesion to the long mould walls, and a large force and rapid opening are important in order to pull the product out of the moulds. To this end use is made of the entire ram surface, where oil supplied by the pressure pump flows into the cylinder, raising the ram- rod and the cross-head with the upper part of the mould at great speed. When the press is opened, the product rises slightly above the mould edge, and an arrangement including pins/fastening elements grips the product so that it follows the upper part of the mould. When the product is lifted out of the lower part of the mould, the cross-head on the ram-rod swings slightly to the side of the mould, and the product is pulled from the upper part of the mould. When pulling the product quickly up from the lower mould-half, the product, which is now hot and elastic, is stretched, thus reducing its cross-section which decreases the pressure and the adhesion to the mould walls.

The columnless double hydraulic press has a large capacity. It has no columns and makes it easier to handle long and heavy mouldings. Furthermore, the costs of this simpler hydraulic press are far lower than those of traditional hydraulic column presses. We shall describe below an embodiment of the invention with reference to the attached drawing, in which B is the hydraulic cylinder with base A. On the lower half of cylinder B is placed/mounted a retaining plate C for retaining a mould-half D. An extended ram-rod G bears a cross-head F. To the latter is secured upper mould-half E. On cross-head F is mounted a gripping arrangement H, which, when the mould is opened, grips the product and holds it fast to the upper mould-half E while pulling the product out of lower mould-half D.

Claims

1) Hydraulic press for producing long pipes and sections etc. preferably from foamed plastic material,

c h a r a c t e r i s e d in that at least on two sides of the lower half of hydraulic cylinder B is secured/mounted a platen C bearing lower half D of the moulding tool, whereas a cross-structure F supporting upper part E of the mould is secured to the top of extended ram-rod G.

2) Hydraulic press for producing long pipes and sections etc. preferably from foamed plastic material, as described in claim 1,

c h a r a c t e r i s e d in that the lower and the upper platen are not joined by columns or stays but only by the ram-rod itself.

3) Hydraulic press for producing long pipes and sections etc. preferably from foamed plastic material, as described in claims 1-2,

c h a r a c t e r i s e d in that upper part E of the moulding tool is secured to cross-structure F in a manner capable of articulation, said cross-structure being pivotably attached to extended ram-rod K.

4) Hydraulic press for producing long pipes and sections etc. preferably from foamed plastic material, as described in claims 1-3,

c h a r a c t e r i s e d in that a sleeve K for supporting crossstructure F is welded/secured to the extended ram-rod.

5) Hydraulic press for producing long pipes and sections etc. preferably from foamed plastic material, as described in claims 1-4,

c h a r a c t e r i s e d in that moulding tool D is kept closed by the back pressure of hydraulic cylinder B and is opened by the main pressure of the ram.

6) Hydraulic press for producing long pipes and sections etc. preferably from foamed plastic material, as described in claims 1-5, c h a r a c t e r i s e d in that gripping arrangements H are secured to pivotable cross-head F on ram-rod G, whereby said gripping

arrangements grip the product when mould D is opened and pull it out of the lower part D of the mould.