Paper making and fiber liberation – Processes and products – Article forming processes
Patent
1998-06-03
2000-10-24
Chin, Peter
Paper making and fiber liberation
Processes and products
Article forming processes
162228, 162380, 162382, 162387, 162388, 162389, D21F 1300
Patent
active
06136150&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of producing a flow of stock in a moulding tank.
The invention also relates to an arrangement in a moulding tank for producing a flow of stock therein, comprising a line, connected to the moulding tank and a machine vat for ready prepared stock, for delivering a fresh stock to the moulding tank by means of a pump which connects with the line.
Moulding tanks of this type are used to produce a fibre product, for example an egg carton or some other packaging product, from the fibres in the stock by means of a male tool with permeable walls and with the aid of a vacuum which sucks the water out of the stock so that the fibres remain on the outside of the tool. In order that the thickness of the fibre layer on the tool and hence the thickness of the product will be as uniform as possible it is essential that the fibre concentration of the flow of stock be as even as possible, at least in the upper areas of the tank.
In a known moulding tank the flow of stock is directed essentially horizontally. Two serious disadvantages arise as a consequence of this direction of flow; on the one hand most of the fibres in the fibre product become oriented in the direction of flow of the stock, which gives the product anisotropic characteristics, on the other the thickness of the fibre layer tends to become greatest where the flow of stock first encounters the tool. Anisotropy in the product means, for example, that it tends to become warped as the product dries out. The underlying reasons for this are well known to the person skilled in the art.
The object of the present invention is to achieve a method of the said type which eliminates the above-mentioned disadvantages. This is achieved according to the invention in that stock is pumped into the bottom of the moulding tank and allowed to flow up over its brim and that the flow of stock pumped in is distributed during its rise in the moulding tank by at least one grating, provided with flow openings and positioned essentially horizontally.
According to a special characteristic of the method according to the invention, a simplified handling of the overflow quantity of stock is achieved in that the overflowed stock is collected and together with fresh stock is pumped back into the moulding tank.
An arrangement of the type described in the preamble, by means of which the method according to the invention can be performed, is characterised in that the line opens in an area close to the bottom of the moulding tank in such a way that an upwardly directed flow of stock is obtained, that the pump is adapted to deliver excess stock so that excess stock can flow over the brim of the moulding tank and that at least one essentially horizontal grating, provided with flow openings, is arranged in the moulding tank.
According to a special characteristic of the invention the arrangement comprises a collecting tank for the excess stock and the pump is adapted to pump the excess stock from the collecting tank together with the fresh stock to the moulding tank, thereby achieving especially advantageous flow paths for the stock.
In order to obtain an optimum dispersal of fibres in the stock the arrangement, as will be apparent from another special characteristic of the invention, comprises two gratings positioned approximately symmetrically in relation to the half-height of the moulding tank, the lower grating having larger through-flow openings than the upper grating but the total through-flow area of both gratings being approximately equal .
The invention will be further explained below with reference to the enclosed drawing in which
FIG. 1 shows an embodiment of an arrangement according to the invention in plan view from the side and
FIG. 2 the arrangement in a plan view from above.
In the drawing 1 denotes a moulding tank for stock intended to be used as described in the preamble. The tank 1 is connected by way of a line 2a to a machine vat, not shown in the drawing, for ready prepared stock. In the embodiment shown in the drawing the tank 1 is surro
REFERENCES:
patent: 1211229 (1917-01-01), Pruyn et al.
patent: 2000085 (1935-05-01), Maginnis
patent: 3043742 (1962-07-01), Chaplin
patent: 3968004 (1976-07-01), Coffey et al.
Celtec Development AB
Chin Peter
LandOfFree
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