Plastic article or earthenware shaping or treating: apparatus – Press forming means – press reshaping means – or vulcanizing... – Cooperating endless belts
Patent
1986-11-12
1988-01-12
Hoag, Willard E.
Plastic article or earthenware shaping or treating: apparatus
Press forming means, press reshaping means, or vulcanizing...
Cooperating endless belts
100 93RP, 100118, 100153, 100154, 1565835, B29C 4342
Patent
active
047188430
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a hot press for continuous treating a continuous web of material which is rolled into rolls or cut into boards, said hot press comprising an upper and a lower press platen, both of which are horizontal, an upper press belt running between the press platens in an upper loop over guide rolls and a corresponding lower press belt running between the press platens in a lower loop over guide rolls, and an upper movable bed of rolling bodies arranged between the upper press platen and the upper press belt, and a lower movable bed of rolling bodies arranged between the lower press platen and the lower press belt, said rolling bodies consisting of solid, elongate cylindrical rods arranged to be conveyed in a course of circuit through the hot press, said press belts defining between them within the region of the press platens a pressing zone having an entry section converging in the direction of movement of the web, for introducing said web.
Due, inter alia, to errors in the shape of said rolling bodies, a corresponding deviation occurs from the precise rolling pattern, causing the relative distance between the rolling bodies to gradually alter during their passage through the pressing zone. Entirely cylindrical rods having different diameters move at half the belt speed without any alteration in the relative distance, but the rods having the smaller diameters roll with higher angular speed. A non-cylindrical rod, e.g. frustum of a cone, will also start to roll at this speed but will gradually be turned until the internal turning torques can no longer balance the frictional forces at the rolling generatrices. The rolling is then combined with a certain sliding or racing which is positive in certain sections of the length of the rod and negative in other sections. The magnitude of the error in shape, friction coefficient and rod diameter determine the effect on the speed of movement. With the rod dimensions generally used, i.e. rods having a diameter of 10-20 mm, the error of shape for a single rod can be kept within a value of well under 0.005 mm at a reasonable cost. For a hot press with a length of up to 25 m, the initial clearance between the rods could then be limited to 1-2 mm.
It has previously been suggested to use rolling bodies which are short in relation to the width of the press and joined together by means of links or the like to a plurality of chains arranged side by side. This prevents the rolling bodies from coming into contact with each other during their passage through the pressing zone. However, a rolling bed constructed in this manner is expensive as well as there being both sliding and roll friction between the rolling bodies and the linearly movable link elements. According to another, more favourable embodiment, the rolling bed comprises rolling bodies in the form of long rods extending across the entire width of the press and connected at the ends to endless conveyor chains which move the rods in a course of circuit through upper and lower loops. The distance or clearance between the rods when introduced into the pressing zone must then be adjusted depending on the length of the press, i.e. the rolling distance, so that a rod cannot roll to catch up the next one in front. The rods must be fed into the pressing zone with an accuracy in the order of 0.5 mm with respect to straightness and positioning. Since the rods are generally 2-3 m in length, and relatively slim, they must be guided at several points along their length when being fed in.
German published specification No. 2.215.618 describes a device in a board press which discontinuously ejects and aligns the rods at right angle to the movement of the steel belts. At the not abnormal speed of 20 m/min for the steel belts, i.e. 10 m/min for the beds of rods, and with a rod pitch of 17 mm, 10 rods per second must be ejected into the board press. This task has proved impossible to carry out in practice. German published specification No. 3.119.529 describes a continuously operating hot press comprising two ste
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Carlsson Bengt J.
Larsson Rolf T.
Hoag Willard E.
Sunds Defibrator AB
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