Press, Particularly For Forming Fiber Plates

Abstract

A press utilizing two pressure platens provides means for measuring the relative distance between the two pressure platens when the platens are in a closed operative position. A signal is generated indicative of the relative distance between the platens and means for varying the flow of pressurized fluid to one or more cylinder piston assemblies connected to a pressure platen is provided. In addition an adjustable rotatable disc carrying spacing pins is provided which permits the adjustment of the relative position of the upper and lower pressure platens.

Description

This invention has for its object a press, particularly for forming fiber plates, which is comprised of two pressure platens located one above the other, one at least of said platens being vertically reciprocatable.

Fiber plates have been manufactured up to now on the present presses in an uneconomical way. Indeed, the outermost layers are made of a generally expensive raw material to which a large amount of glue is added to give to the fiber plates a hard closed outer surface. This expensive raw material is comprised of thin fibers which are prepared in a particular way by means of heavy shaving machines the output of which is very low. After the pressing of the various raw materials into a plate, such plate is brought to a desired constant thickness by means of expensive sanding machines with high output and a large consumption of sanding belts. An important part of the expensive outer layers is removed by these sanding machines.

The invention has for purpose to obviate these drawbacks by providing a press which allows to obtain a fiber plate which has directly the desired constant thickness in every cross section thereof and which thus does not have to be brought to the desired thickness by sanding, which means an enormous saving both in machines and raw material.

By using the press according to the invention, the preparation of the fibers is very much simplified. The fibers may have a thickness up to 0.4 mm., whereby the output of a shaving machine may largely be increased. As no sanding is required after the pressing, the thickness of the outer layers may be reduced to a minimum and it is generally sufficient to use for the making of these outer layers, the fine fibers which are found in waste products. The amount of glue used is also much reduced.

For this purpose, on the press according to the invention, means are provided for maintaining constant, within predetermined limits, the spacing between both pressure platens over the whole width thereof during the press operation.

Usefully, in an hydraulic or pneumatic press with pistons acting upon at least one of the pressure platens, the said means have at least one regulating device which cooperates at least with those pistons located centrally relative to the pressure platens and allows to act automatically upon said pistons according to an adjusted spacing between the pressure platens.

In one embodiment of the invention one of the pressure platens has independently operating detectors which cooperate with the regulating devices. Each detector reacts to a spacing differential due to a distortion of at least one pressure platen and transmits an impulse proportional to the spacing differential to the corresponding regulating device. The regulating device is coupled to one or more pistons located immediately adjacent a detector and causes a pressure change proportional to the pulse until the desired spacing between the pressure platens is reached.

Other details and features of the invention will stand out from the description given below by way of nonlimitative example and with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic showing of a press according to a first embodiment of the invention; and

FIG. 2 is a diagrammatic showing of a press according to a second embodiment of the invention.

In both figures, the same reference numerals pertain to similar elements.

In FIG. 1 is shown a front view of a press for the shaping of fiber plates which according to the invention, allows during the pressing of a fiber cake, to control the thickness thereof in various points of the press in a continuous way and to compare same with a previously adjusted value, to operate the possibly required corrections. Without such a control, it is substantially impossible to obtain, from some width of the press upwards, plates with a constant thickness. This is to be imputed to the distortions of the pressure platens resulting from the heat and the pressure to which these platens are subjected.

The press according to the invention is comprised of two heated pressure platens 1 and 2 located one above the other, among which the lower platen 1 bears on the frame 3 of the press through diabolo-shaped supports 4, so as to limit the heat transfer from the pressure platen 1 to the frame 3 and the upper platen 2 is reciprocatable vertically by means of a series of pistons 5 cooperating with said platen 2, which pistons are movable inside cylinders 6 fixed relative to the frame 3 and which determine the required pressure between the platens 1 and 2.

The above-mentioned control occurs by means of an electronic apparatus, which is only shown partially, and which has been used mostly up to now for determining the thickness of the fiber plates leaving the sanding machines which have been mentioned above.

This apparatus is mainly comprised of a series of detectors 7 which contact the outer surface of the upper pressure platen 2 and which may follow the distortions thereof. Each detector 7 is mounted on a regulating and measuring instrument 8 which is coupled to the adjacent piston(s) 5.

The regulating and measuring instruments 8 are distributed over U-shape beams 9 which extend, in parallel relationship with one another, over the whole width above the pressure platen 2. Against the outer side of the lower platen 1, immediately below the beams 9, are arranged similar beams 10 which are pushed by means of springs 11 against the platen, in such a way that the beams 10 follow every distortion of the lower platen 1. On that side of the beams 10 which is directed towards the pressure platen 1, are present adjusting screws 12 which determine the spacing between the beams 10 and the pressure platen 1. The contact point of the adjusting screw 12 with the platen 1 always lies substantially on the vertical line that passes through the contact point of a detector 7 with the platen 2. The spacing measured by an instrument 8 is the spacing between the contact point of the corresponding detector with the platen 2 and the underneath-located contact point of an adjusting screw 12 with the platen 1.

The desired spacing between the platens 1 and 2 may be adjusted. When during the pressing of a fiber cake 13, in some particular location of the pressure platens 1 and 2, there occurs a spacing change relative to the adjusted spacing, the detector 7 which lies in this location, transmits a pulse proportional to such change to the corresponding regulating and measuring instrument 8, which in turn determines a pressure change proportional to said pulse, for the piston(s) 5 in said location until the adjusted spacing between the pressure platens 1 and 2 is again reached in said location.

During the pressing of a fiber cake 13 between both pressure platens 1 and 2, the hydraulic pressure on the pistons 5 is increased as long as the required thickness of the cake 13 has not been reached. As soon as this thickness is reached the pressure on the pistons 5 is maintained constant. This results, notwithstanding the retaining of a constant pressure on the pistons 5, in the thickness of the cake 13 being further reduced after some pressing time, and thus coming below the desired thickness. At this moment, through the detectors 7, the regulating and measuring instruments 8 are operated and by means thereof, the pressure on the various pistons 5 is systematically reduced so that the thickness of the cake 13 is changed but within very narrow limits. Thus it is possible in this way to form fiber plates in which the largest differential between the adjusted thickness and the ultimate thickness of a fiber plate formed in the press according to the invention, is 0.2 mm.

As the pressure on the platen 2 is regulated from place to place according to the spacing between the platens 1 and 2, these latter ones may be somewhat flexible and thus less thick than in the present presses.

In the above-described press, gauges (not shown) which are comprised of prisms with well-determined thicknesses, are used or not for the adjusting of the desired thickness of the fiber cake.

When using gauges which are arranged between the side edges of the pressure platens, no pressure regulation must be provided for the pistons 5 which work adjacent said edges as in this location substantially no distortion of the pressure platens 1 and 2 is possible.

If the outermost pistons 5 also cooperate with a regulating instrument 8, the gauges may be dispensed with and a spacing adjustment may be provided between the mutually facing ends of the U-beams 9 and 10. Such an embodiment is shown in the drawings. On both vertical legs of the lower beam 10 is mounted a disk 14 rotatable about a vertical axis. This disk 14 bears on the upper side thereof, on the edge of the disk, spacing pins 15 of different length, which extend in parallel relationship with said axis and which may be brought separately, by a rotation of the disk 14 over some determined angle, between the facing ends of the beams 9 and 10 so as to determine the desired spacing between said ends and consequently between the pressure platens 1 and 2. Because a good contact of the beam 9 with the spacing pins 15 should be provided, the vertical parts of the beam 9 are guided in side extension pieces 16 of the pressure platen 2 and a spring 17 is provided between these extension pieces 16 and the free end of the beam 9.

The dispensing of the gauges further gives to the press according to the invention an additional precision. There is always a danger that foreign materials set down on the gauges. The removal of the gauges also gives an important advantage as regards work saving and output increase. The replacement of the gauges must be made with great accuracy and requires much time, which thus goes together with an important production loss.

By using suitable regulating and measuring instruments 8, the mechanical spacing adjustment between the beams 9 and 10, as shown in the figure, may even be dispensed with. In such a case, the corresponding ends of beams 9 and 10 are pushed against one another by means of the springs 17 and the instruments 8 should have a measuring range which covers the complete thickness of the pressed fiber cake. In both other cases, where there first occurs a mechanical adjustment of the desired thickness by means of gauges or of a disk 14, the measuring range of the instruments 8 only has to cover the possible variations in the thickness relative to the adjusted value. The instruments 8 will work in these latter cases with a higher accuracy.

In still another embodiment of the invention which is shown in FIG. 2, detectors 7 are provided together with regulating instruments 8 both on the pressure platen 2 and on the pressure platen 1. The regulating instruments 8 which are to cooperate with the upper pressure platen 2 have, as the ones mentioned above, a measuring range which is large enough to cover the complete thickness of the cake, while those regulating instruments which cooperate with the lower pressure platen 1 have a smaller measuring range as they only have to follow the distortions of said platen 1. Two regulating instruments with detector contact points which are located on the same vertical line then form a regulating unit by differential measuring. In this last embodiment, the pressure platen 1 bears no more on fixed adjusting screws but rather on detectors 7 of regulating instruments 8.

The above-described spacing pins between the beams 9 and 10 for determining the thickness are also dispensed with. They may be replaced by an electronic adjustment.

Such electronic adjustment may possibly be combined with gauges 20 which are arranged between the edges of the pressure platens 1 and 2. In such a case, the gauges only serve to determine the thickness of the portion of the cake adjacent the edges thereof, while the electronic adjustment is designed to regulate the thickness of the center portion of the cake.

If the gauges are dispensed with, the electronic adjustment also serves to regulate the thickness of the cake at the edges thereof.

The beams 9 and 10 further form together a closed framing about the pressure platens 1 and 2, which are movable within certain limits independently of said framing.

It must be understood that the invention is in no way limited to the above embodiments and that many changes may be brought therein without departing from the scope of the invention as defined by the appended claims.

For instance, one may use as regulating and measuring instruments, any device which enables to reach the object mentioned above. The regulating and measuring instruments may act in another way than by pressure regulation on the pistons of the press for maintaining constant the spacing between the pressure platens.

Claims

I claim:

1. A press particularly for shaping fiber plates comprising two pressure platens;

means for supporting the two pressure platens including a lower supporting base, a U-shaped beam and a revolving disc carrying a plurality of spacing pins extending perpendicular to the plane of the disc, the spacing pins locating the U-shaped beam relative to the lower supporting base;

a plurality of cylinder piston assemblies operatively connected with at lease one of the platens for exerting pressure at regularly dispersed points on the exterior face of the platen;

means for supplying pressurized fluid to the cylinder piston assemblies;

means for measuring the relative distance between the two pressure platens when the platens are in a closed operative position including a detector located adjacent the operative connection of each cylinder piston assembly with the platen for generating a signal indicative of the relative distance, each detector providing a signal which permits the adjustment of the pressurized fluid flow to the cylinder piston assembly located adjacent the detector, and

means for varying the flow of pressurized fluid to each cylinder piston assembly adjacent a respective detector in response to the signal for maintaining a relative distance between the platens.

2. A press as in claim 1 wherein means for adjusting the lower platen is provided on the lower supporting base on the same vertical plane as the connection of the cylinder piston assembly with the platen.

3. A press as in claim 1 wherein the means for supporting the two pressure platens further includes heat-isolating legs attached to one of the platens and spring means supportably attached to the lower supporting base.

4. A press particularly for shaping fiber plates comprising two pressure platens;

means for supporting the two pressure platens including a lower supporting base and a U-shaped beam, each operatively connected to a pressure platen;

means for positioning the U-shaped beam relative to the lower supporting base;

a spring connecting the U-shaped beam to its pressure platen adjacent the means for positioning the U-shaped beam;

a plurality of cylinder piston assemblies operatively connected with at least one of the platens for exerting pressure at regularly dispersed points on the exterior face of the platen;

means for supplying pressurized fluid to the cylinder piston assemblies;

means for measuring the relative distance between two pressure platens when the platens are in a closed operative position including a detector located adjacent the operative connection of each cylinder piston assembly with the platen for generating a signal indicative of the relative distance, each detector providing a signal which permits the adjustment of the pressurized fluid flow to the cylinder piston assembly located adjacent the detector, and

means for varying the flow of pressurized fluid to each cylinder piston assembly adjacent a respective detector in response to the signal for maintaining a relative distance between the platens.