Manufacture of insulating products

Abstract

A filter press, e.g. for the manufacture of insulation products from an aqueous slurry, which has a number of movable platen portions. The platens have individual actuating means which are adjustable relative to one another but are controlled by a common drive which can move all the portions simultaneously as one platen.Also the method of using the press for the manufacture of insulation products. SUThe present invention relates to the manufacture of sheet or slab form insulation products from relatively free flowing slurries, for example containing calcium silicate and/or fibre. In particular it relates to a filter press which can be used to make such products. It also relates to a method of making sheet or slab form insulation products.Such products may be made by paper and/or board making techniques, they may also be made by filter pressing in which a measured volume of slurry is poured into a foraminous mould cavity and then de-watered by pressing.Conventional platen presses can be used for this, but uneven pressure distribution and fluid leakage around the edges of the press platen tend to give a product of irregular thickness and density.It is an object of the present invention to provide an improved filter press for manufacturing such sheet or slab form insulation products and it is a further object of the invention to provide an improved method for use with this press.According to the invention, a filter press includes a plurality of movable platen portions, each with individual actuating means which are adjustable relative to one another, but which are also controlled by a common drive arranged and adapted, in operation, to move all the platen portions substantially simultaneously as a single platen.Preferably, the press further includes means defining a mould cavity, said means comprising sidewall members movable into and out of substantially sealing relation with the periphery of the platen portions as a whole together with an endless filter band so disposed as to constitute a face of the mould cavity directly opposed to the platen portions. Preferably, one sidewall member is also moveable in a direction away from the filter band so as to enable advancement of the filter band to carry a product out of the mould cavity. The filter band may be arranged to discharge the product onto a conveyor belt provided with length/width trimming apparatus for the product.Advantageously, the platen portions are arranged end-to-end lengthwise of the press, each platen portion having a width substantially equal to the width of the product to be made, the length of the press being its dimension in the direction of travel of the endless filter band. The individual actuating means may be screw jacks driven by a common drive shaft, to ensure that once the jacks have been adjusted to produce a product of uniform thickness, this setting will be accurately repeated for each succeeding product. Preferably at least four jacks are provided for each platen portion.The use of screw jacks and a common drive shaft has the added advantage that the platen portions can be stopped at any point in their range of movement, without the need for fixed limit stops, as in a conventional platen press. It follows that all of the available pressure is applied to the product and not directly to the hardware of the press, thus allowing preselection of the finished product thickness.Furthermore, the density of the product can also be controlled by adjusting the position of the platen portions prior to pumping the slurry into the mould cavity.It should be noted that having made one sheet or slab, the platen portions can be raised to create a new mould cavity on top of the first sheet or slab. A second sheet or slab can then be made on top of the first, using the same or a different slurry. It is thus possible to form laminated products wherein each layer is of different density and/or composition to the next layer.According to a further aspect of the present invention, a method of manufacturing sheet or slab form insulation products from an aqueous slurry containing calcium silicate and/or fibre comprises pumping the slurry into a closed mould cavity in a platen filter press, at least one wall of the mould cavity being foraminous to an extent sufficient to allow the escape substantially only of fluid, stopping the pumping at a predetermined level of back pressure in the mould cavity, followed by closing the press to reduce at least one dimension of the mould cavity a prechosen amount.Positively pumping the slurry into the mould cavity up to a predetermined level of back pressure achieves firstly, a higher solids content in the mould cavity, coupled with a degree of de-watering prior to pressing. Secondly it makes for an improved control of both product density and regularity, since the volume of solids in the cavity prior to pressing can be controlled by selecting the appropriate back pressure.The problem of leakage around the platen of a conventional platen press can be minimized by making the platen a close fit within the walls of the mould cavity. The latter may be simply a rectangular frame constituting four side walls, the bed of the press constituting the bottom wall and the platen constituting the top wall of the cavity. The bottom wall, that is the press bed, may be a filter cloth stretched over an apertured backing plate and the filter cloth may be in the form of an endless band or it may be static, but in either case removal of the product after pressing can be effected by raising the press platen clear of the cavity side walls prior to sliding the mould cavity out of the press. Where the mould cavity is in the form of a rectangular frame the method of the invention preferably therefore includes the additional step of opening the press at least sufficiently to enable the mould cavity to be withdrawn and/or inserted into the press, an appropriate. It should be noted in this context that the slurry is most conveniently supplied to the mould cavity through a supply aperture in the side walls of the cavity.The desired back pressure can be controlled by using air pressure as the pumping medium, for example, by pressurising with air a stock chamber which supplies the mould cavity. When the back pressure in the mould cavity reaches the level of the air pressure the flow will naturally cease and this may be monitored either by suitable instrumentation or visually by an operative.Although conventional filter presses can be used with relatively minor modifications to carry out the method of the invention, they tend to be massive in construction, especially where pressure has to be applied evenly over a large area to make a product of sensibly constant thickness. The use of fixed limit stops to control platen displacement inevitably results in the press frame being subjected to very heavy loading and it must, therefore, be built to withstand such loading.It is therefore preferred that a filter press according to the present invention be used to carry out the method, particularly as the position of the platen portions can be adjusted to control product density, in addition to the control already effected by adjustment of the back pressure.

Description

Claims

1. A filter press for making sheet products from a liquid slurry comprising:

(i) a plurality of movable platen portions disposed end-to-end lengthwise of the press to form a single unitary surface

(ii) a filter material opposite said unitary surface

(iii) a plurality of individual screw jack actuating means, for each platen portion, adjustable relative to one another

(iv) a common drive shaft connected to all of said screw jack actuating means, for movement of all of the platen portions substantially simultaneously as a single platen

(v) sidewall means defining, with said plurality of platen portions and said filter material, a single mould cavity.

2. A filter press according to claim 1 in which the actuating means for each platen portion is at least four screw jacks.

3. A filter press for making sheet products from a liquid slurry comprising:

(i) a plurality of movable platen portions disposed end-to-end lengthwise of the press to form a single unitary surface.

(ii) a plurality of individual screw jack actuating means, for each platen portion, adjustable relative to one another,

(iii) a common drive shaft connected to all of the screw jack actuating means, for movement of all of the platen portions substantially simultaneously as a single platen,

(iv) a plurality of sidewall members swingably movable into and out of substantially sealing relation with the periphery of the plurality of platen portions,

(v) an endless filter band opposed to said plurality of platen portions, said sidewall members and said endless filter band, together with said plurality of platen portions, defining a single mould cavity.

4. A filter press according to claim 3 wherein one sidewall member is also moveable in a direction away from the filter band so as to enable advancement of the filter band through the press to carry a product out of the mould cavity.

5. A filter press according to claim 3 wherein each of the platen portions have drain channels defined by upstanding walls extending from the platen portion surface opposite the filter band, said surface further have aperatures extending through the surface and in communication with said drain channels and said surface is covered by a filter cloth to form a liquid permeable surface for draining liquid expressed through the surface.

6. A filter press according to claim 5 wherein said drain channels extend lengthwise of the press and wherein said channels slope at an angle to the horizontal so that expressed liquid tends to drain from the channels to one end of the press under gravity.

7. A filter press, according to claim 3, wherein each platen portion has a width substantially equal to the width of the product to be made.

8. A press according to claim 3 in which the movable sidewall members are hinged.