Plastic article or earthenware shaping or treating: apparatus – With mechanical means forming or expanding pores
Patent
1995-02-02
1996-12-10
Warden, Jill
Plastic article or earthenware shaping or treating: apparatus
With mechanical means forming or expanding pores
425817C, 425223, 425224, 264 458, 264 462, B29D 700, B29C 3916
Patent
active
055828400
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for the continuous manufacture of slabstock polyurethane foam comprising conveyor means, a mixing head for mixing polyurethane reaction components containing a blowing agent, means for discharging said reaction mixture onto said conveyor means and means for driving said conveyor means.
Such a device is generally known. In practice, use is made of different types of continuous foaming machines including the conventional inclined conveyor machines, either with or without planiblock, maxfoam and varimax machines. A problem with these known continuous foam production machines is that a manual operation is required as well at the beginning of a foam production run as at the end thereof in order to obtain a useful front and end portion of the slabstock foam. Without the manual intervention of an operator, both the first and the last foam portion of a production run would decline slowly to the respective extremity of the slabstock foam resulting in a loss of several meters of foam.
In the known machines, the operators use for example a board fixed at the end of a long pole to retain the first portion of reaction mixture while they stand on the first conveyor. As the conveyor starts running, the start board retaining the foaming reaction mixture moves also over the conveyor means. At the end of a production run, the operators push the last portion of reaction mixture forwards in order to obtain an end portion of the desired height.
A drawback of the known devices consists in that in some cases the operators have to enter the foaming machines both at the start and at the end of a production run to realize the desired foam profile. It is clear that this may be dangerous and harmful to their health due to the production of noxious gases during the foam process.
Moreover, the obtained foam profile depends on the skill and experience of the operator. In fact, the operator has no direct control of the foam height but the effect of the manual manipulation of the foaming reaction mixture can only be seen after a certain time, more particular after the time required by the foam to reach its final height. Further, the rise process of the reaction mixture depends on its composition, and more particularly on its blowing agent content, so that this composition has also to be taken into account when manipulating the reaction mixture to obtain the desired foam profile.
An object of the present invention is to provide a device for the continuous manufacture of slabstock polyurethane foam which allows control of the foam profile at the beginning and the end of a production run without requiring operators to enter the foaming machine and which optimises the start and end profile of the foam blocks.
To this end, a device according to the invention is characterised in that it comprises moreover a start board and a stop board, means for positioning said start board transversely onto said conveyor means near the place of discharge of said reaction mixture at the beginning of a production run, means for moving the start board along said conveyor means in such a manner that the start board obstructs, in a first phase, the reaction mixture moving over said conveyor means to thereby increase the height of the front portion of the produced slabstock polyurethane foam more particularly so that this front portion will substantially have the same height as a subsequent portion after full rise expansion, and in such a manner that it moves, in a second phase, substantially at the same speed as said conveyor means, means for removing the start board from said conveyor means after the front portion of the produced foam retains sufficiently its shape, means for positioning the stop board transversely onto said conveyor means near the place of discharge of said reaction mixture after the reaction mixture discharge is stopped, means for moving the stop board along said conveyor means after the positioning of said stop board so as to push the foaming reaction mixture ahead relative to said conveyor means to th
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Blackwell Brian J.
Evers Robertus H.
Mortelmans Rudi
Pauw Hendrik
Dawson E. Leigh
Prefoam AG
Warden Jill
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