US3356014A - Method for continuous pressing - Google Patents

Description

1967 N. R. ALENIUS METHOD FOR CONTINUOUS PRESSING 5 Sheets-Sheet 1 Original Filed Oct.

Md I

INVENTOR.

Nils Robert Alenius ATTORNEYS Dec. 5, 1967 R. ALENIUS 3,356,014

METHOD FOR CONTINUOUS PRESSING Original Filed Oct. 1, 1962 5 Sheets-Sheet 2 FIGS BY Nils Roberr Alenius ATTORNEYS Dec. 5, 1967 Us 3,356,014

METHOD FOR CONTINUOUS PRESSING Original Filed Oct. 1, 1962 3 Sheets-Sheet 5 FIG. 9

v INVENTOR.

Nils Robert Alenius ATTORNEYS UnitedStates Patent 2 Claims. (Cl. 100-35) ABSTRACT OF THE DISCLOSURE Method for continuous pressing especially applicable to the pressing of materials produced in the form of a continuously progressing, unbroken mat.

This application is a division of my application Ser. No. 227,470, filed Oct. 1, 1962, entitled, Apparatus for Continuous Pressing, and now United States Letters Patent No. 3,202,090, issued on Aug. 24, 1965.

This invention relates to a method for continuous pressing which is especially applicable to the pressing of materials produced in'the form of a continuously progressing, unbroken mat. Materials for which this kind of pressing is suitable include different types of wooden and fibrous boards, plywood, laminated panels, composite boards, etc. The pressing operation, as contemplated by the invention, is carried out during the continuous travel of the mat of material, and is effected by a mobile press in such a way that after the completion of the pressing operation the-material still comprises an unbroken, continuous mat from which may be cut the panels desired. It is obvious that this type of pressing offers many advantages over the traditional method of batch pressing, a fact commonly recognized by the trade. By continuous pressing, very considerable savings are made both as re gards material and labour and other production costs; in addition, one valuable advantage gained is that the final panels, contrary to what is possible in traditional practice, can be had in any length irrespective of the length of the press used.

It is known that the art of continuous pressing may be employed by the use of stationary presses in which the pressure is eifected by means of press plates which consist of either a pair of travelling, endless pressing belts, or oscillating superimposed pressing plates or rails. However the practical value of these presses is almost entirely destroyed by the technical disadvantage that the total pressing power of the mobile pressing elements must be derived from the stationary press frame. The transference of the immense power required for the pressing can be accomplished only by the intermediation of friction reducing rolls, bearings or similar means, but this expedient makes the construction of the presses very intricate and expensive, and seriously complicates their operation and maintenance. The disadvantages of this constructional drawback are in fact so considerable that this type of press has found no practical use in the industry concerned with the manufacture of boards and panels.

It is an object of this invention to provide a method by which the advantages of continuous pressing can be achieved in a simpler, more practical, and less expensive way than that described above. The principal feature of this method is that the progressing material mat to be pressed is conveyed through a .press between its press plates; this press is mobile, and is moved forwards and backwards in the direction of movement of the material mat in such a way that the forward movement of the press, which corresponds in direction to that of the material mat, and during which movement the section of the material mat within the press is being pressed, is

synchronous with the progress of the material during the act of pressing. Subsequent to completion of the pressing, the backward movement of the press returns it to the starting point of its forward movement, thus enabling the operation cycle to be repeated on the next section of the mat of material to be pressed.

Another object of the present invention is the provision of an apparatus for the implementation of the pressing method indicated above. In its general embodiment, the apparatus comprises a one-opening sheet press, mobile on a track, between the press plates of which is conveyed the progressing material mat, and which press is moved forwards and backwards in the travel direction of the material mat in such a way that the forward movement of the press, which corresponds to that of the material mat, and during which movement the section of the material mat within the press is being pressed, synchronizes the progress of the material mat during the act of pressing; the backward movement of the press after the completion of the pressing returns the press to the starting point of its forward movement, in order to enable the operation cycle to be repeated on the next section of the mat of material to be pressed.

A further object of the invention is that of providing a simple and reliable means of attaining absolute synchronization between the forward, pressing movement of the press and the travel of the material, as even the slightest deviation with respect to the speed could prove injurious to the unpressed material in front of the press. According to the invention this important feature of the process is controlled by having the forward movement of the press, is. that of the direction of travel of the material, caused by a force which continuously and independently of the rate of travel of the press tries to move the press at a greater speed than that of the material, but which is checked by a blocking device operating in unison with the progress of the material, and bringing the movement of the press into complete synchronization with the travel of the material mat. Consequently, the force which effects the forward movement of the press must be of yielding and flexible nature. Means for the provision of this kind of force include a pneumatic motor or pressure cylinder, a hydraulic motor or piston provided with an overflow valve, an alternating current motor connected with a sliding coupling, a direct current motor, or a suspended weight which acts on the press or on its drive by means of a wire.

Other objects and advantages will appear in the following description, and the novel features of the method are particularly pointed out in the claims appended.

This invention is described in the followng with reference to the enclosed drawing, which schematically shows an embodiment of the invention.

FIG. 1 is a side elevation of the mobile press and its track;

FIG. 2 shows the press in cross section through IIII of FIG. 1;

FIG. 3 is a plan view of an embodiment of the drive and the power transmission for the forward and backward motion of the press;

FIG. 4 is a partial side elevation of the drive shown in FIG. 3;

FIG. 5 is a side elevation view of another embodiment of the power transmission shown in FIG. 3;

FIG. 6 is a similar view of another form;

FIG. 7 is a plan view of another embodiment of the drive for the forward and backward motion of the press;

FIG. 8 illustrates a detail of the control equipment, which enables maneuvering of the forward and backward movement of the press; and

FIG. 9 is an end elevation of another embodiment of 3 the mobile press having tanks for the provision of heating and cooling agents.

If similar details are shown in different figures, they have the same reference symbols.

The press shown in FIGS. 1 and 2 comprises a frame constructon 1 furnished with a pair of superimposed press plates '3 and 4, of which plate 4 is fixed to the frame construction, whereas plate 3 is vertically movable by the aid of hydraulic jacks 18, in their turn controlled by pump equipment 19 driven by electromotor 20. Press frame 1 is mounted on a number of Wheels 5, which enable the press to be moved forward and backward in press track 6. The continuously travelling material, on a carrier band or alone, indicated by dash lines 2, is conveyed between pressplates 3 and 4, the direction of travel of the mat here being that of the forward stroke of the press. Through a drive, whose construction is described below, the movements of the mobile press are etfectuated so that at the beginning of the forward stroke, the press is at the right end of the track according to FIG. 1, it is then accelerated to the speed of the travelling material mat, and once it has reached it, hydraulic jacks 18 are actuated in order to tighten the press plates against the material mat. The press is then moved synchronously with the travel of the mat for a distance which corresponds to the pressing time, and following this, the press having reached the end of the forward stroke at the other end of the track, the pressure of the jacks is released and the press plates separated. This done, the press is removed to the starting point of the forward stroke, and the operation cycle repeated. In order to shorten the time of the cycle, the return stroke can be elfectuated at a speed higher than that of the synchronous forward movement. The length of the press and its travelling stroke are so dimensioned in relation to each other that each pressing stroke somewhat overlaps the section pressed at the preceding stroke, resulting in the material mat being pressed without a break over the whole of its length.

In order to speed up the act of pressure, the press plates are heated, and are to this end furnished with borings 17 through which is passed a heating agent. The agent, if a liquid or gas, is transmitted to the press plates from a stationary source by means of flexible tubes, toggle joint pipes, or similar devices, which are capable of following the press in its motion forward and backward. In the embodiment according to FIG. 1 the heat transference is made by means of toggle jointed pipes 8 and 9. The stationary ends of the pipe systsem are mounted on a mast construction 7 bridging the press track.

Another way of having a fluid heating agent conveyed to the mobile press is shown in FIG. 9. According to this method, the heating agent is provided in an open, long tank '51 located along the track of the press. From this tank, irrespective of the movement of the press, the heated liquid is conveyed to the press by pump 52, and after circulation, is let back into the tank for reheating. Of course, forthis kind of heat conveyance, it is necessary that the liquid is used at a temperature below its boiling point.

At the infeed end of the press, at the right in FIG. 1, where the material mat is inserted between the press plates, the plates may be cooled when heat setting adhesive is used for the bonding of the material. This is designed to prevent the adhesive outside the press, not subjected to pressure, from being prematurely set due to heat radiation from the press plates. The cooling is suit ably carried out by conducting a cooling agent through borings in the infeed end of the plates. According to the embodiment illustrated in the figures, the agent is conveyed to the mobile press by means of flexible tubes attached to pendling toggle joint pipes 8 and 9.

During the forward and backward movements of the press, parts of the material mat above the press track are unsupported by the press, and are consequently liable to excessive deflection. To prevent this, the press track is furnished with a number of movable rolls 11, which suit ably distanced support those parts of the material mat over the track which are not carried by the press. The rolls ride on rails 12 along the press track, and are connected to each other as well as to the press by means of chains or similar means 13, which enable the rolls to be alternatively moved closer to or further away from each other in accordance with the movements of the press.

If for some reason the material mat did not properly disengage from the press plates at the opening of the press, this at the start of the return movement cause damage to the unpressed material in front of the press. This risk is eliminated by the press track having a special locking device, which on the one hand prevents the material from moving in reverse, and on the other hand disengages the material from the press plates at the start of the return movement. This device may consist of a pair of friction rolls, situated at the outfeed end of the press track between which the material mat is passed; these rolls have their rotation barred so that the material 'mat is allowed to move in its forward direction only. The locking device may also, as shown in the figure, include pivoted stoppers 15; if the material mat is moved backwards, these instantly engage as a result of friction and lock the material.

FIGURES 3 and 4 show an embodiment of the drive which effects the forward and backward movements of the press. These movements have to be carried out according to an exact scheme, which requires that the return movement, notwithstanding the mass of the press, has to be carried out in the shortest possible time, whereas the forward movement has to take place at the rate of the travelling material, irrespective of its speed variations, and additionally in absolute synchronization with it. These demands on the versatility and precision of the movements are met by the drive described below. Starting with the return movement, this is according to the embodiment actuated by electromotor 21, which acts upon drum 26 on shaft 25 over gear 23, 24, and which action is controlled by means of magnetic coupling 22. Wire 27, which is wound on drum 26 has its ends 28 and 29 attached to the press as illustrated in FIG. 1, transfers the power from shaft 25 to the press. The forward movement of the press is according to the embodiment actuated by weight 14 (see FIG. 1) which by means of wire 30 is suspended in mast 7 and revolves drum 31 on shaft 25 in a direction opposite to the rotation corresponding to the return movement of the press. The mass of weight 14 is dimensioned so that it can accelerate the press. The two counteracting power sources, electromotor 21 and weight 14, make the motion cycle of the press proceed as follows. Before the end of the return stroke and at a distance equal to the retardation stretch of the press, determined by its mass, its travelling friction and the counteraction of weight 14, elec- D tromotor 21 is disengaged and the press allowed to proceed by its motive energy until the return movement is completed. Nevertheless, owing to weight 14, after the dead point the press automatically begins moving in the opposite direction, i.e. that of the forward stroke. The weight causes, the press to accelerate, and at the point where the acceleration reaches the speed of the travelling material mat, its motion is barred by a blocking device, which allows the press to move at the speed of the travelling mat only, thereby enabling the press to be closed on the material mat. For the sake of simplicity, this blocking device is shown in the figures in the form of a ratchet wheel with a co-acting pawl. The ratchet wheel, indicated by reference 34, is fixed on shaft 25, and allows this to revolve freely with respect to the pawl, reference 35, in a direction corresponding to that of the return stroke of the press. Pawl 35 is mounted on sprocket wheel 32, which by means of chain drive 33 is connected to the drive which causes the travel of the material. This travelling and the rotation of the pawl are thus operated by the same source of power, i.e. by the drive causing thetravel of the material mat, by reason of which the two movements can be made to coincide. Accordingly, during the forward, pressing stroke the press has to travel at a rate which is synchronous with that of the material mat from the moment the ratchet engages the pawl, as the travel of the press, as well as that of the material mat, is subsequently controlled only by the drive which causes the material mat to travel. After the completion of the forward stroke, the press is returned by motor 21 to the starting point of the forward movement, and as ratchet wheel 34 is free to move with respect to pawl 35, the return can be made at any speed desired. The rotation of shaft 25 during the return movement hoists weight 14, and thus there is stored new energy for the succeeding forward movement.

FIG. 5 shows a modification of the driving equipment illustrated in FIG. 3; here, wire drum 26 is replaced by a sprocket wheel 126, and wire 27 by a chain 127. The ends of the chain 127 are attached to the press in the same way as the ends of the wire 27.

FIG. 6 shows still another modification, in which the drum and wire shown in FIG. 3 are replaced by gear wheel 226 engaging rack 227 attached to the press.

The drive arrangement shown in FIG. 7 differs from that of FIG. 3, as the electromotor and the weight are replaced by a double acting hydraulic or pneumatic pressure cylinder 36, by which rack 37 is driven forward and backward. Rack 37 actuates rack 3-8 attached to the press by means of spur gearing 39, 46. The blocking device which ensures the synchronous motion of the press and the material mat during the pressing operation, and which allows the faster return motion of the press, corresponds substantially to the blocking arrangement indicated by references 32, 33, 34 and 35 in FIGS. 3 and 4. In order to avoid an impractically long operation stroke of pressure cylinder 36, gearing 39, 40 is dimensioned so that rack 38, i.e. the press, moves the desired distance, even if the stroke of rack 37 is shorter. This possibility is indicated in the draWing by showing gear wheel 40 considerably larger than gear wheel 39.

Of course, it is also possible to arrange the forward and backward motion of the press by means of hydraulic pistons which act directly on the press, and with strokes that correspond to the travelling distance of the press. However, in most cases, this construction is uneconomical and difiicult to realize, as the travel distance of presses of this type is seldom below meters, and the construction of pressure cylinders for strokes of these lengths involves very intricate technical problems.

For big and heavy presses, short pressure cylinders or jacks are suitable as supplementary sources of power in addition to the drive arrangement shown in FIGS. 3-7. For the acceleration and retardation, of the press, especially for the return stroke, considerable expenditure of force is required because of the substantial mass of the press. To obviate the necessity of having the ordinary drive dimensioned to deal with these forces which are needed only momentarily and are many times greater than the force required for the uniform travel of the press, it is of advantage to have the acceleration and the retardation effected by special pneumatic or hydraulic pressure cylinders, or jacks 41 and 42 mounted on the track as shown in FIG. 1. When the press is to be accelerated at the beginning of its return stroke, a pressure agent is led into cylinder 41 by means of an inlet valve, and thus the piston of the cylinder actuates the press and increases its velocity to the rate desired. At the other end of the press track, where the press has to be retarded, the motive energy of the press can be absorbed by suitable throttling of the pressure agent in cylinder 42. By connecting the cylinders or jacks 41 and 42 to each other by the way of an accumulator, the kinetic energy absorbed from the press at retardation can be stored :by the accumulator 53, and then used again for the subsequent acceleration of the press. In this way no external power is required in order to carry out the heavy work entailed by the accelerationand retardation of the press.

FIG. 8 shows schematically a detail of the control arrangement by which are maneuvered the movements of the press and the press plates. The control is effected according to the embodiment by means of electrical impulses emitted by limit switches located along the track. Here, a special problem is posed by the impulse for the closing of the press at the beginning of the forward movement. As the press cannot be closed before its travel coincides with that of the material, prior to its closing the press has to move a distance which corresponds to the acceleration of the press after its halt at the turning point. As during its return movement the press is subjected to the influence of varying, external forces, the location of the turning point may differ somewhat from one operational cycle to another; as a consequence there is no guarantee that the necessary distance of acceleration is available on each occasion. In order to eliminate this risk, a special arrangement for the control system is essential. This arrangement is shown in the figure, where reference 43 indicates a rail attached to the track at the side of the press. On this rail there rides a cam 44 which is movable on the rail so that the sliding of the cam requires more force than does the actuating of limit switch 47 with which the cam co-operates. The sliding of the cam is efiectuated by pushers 45 and 46, which, like limit switch 47, are attached to the mobile press. The arrangement functions as follows: the figure illustrates the situation at the turning point of the press, prior to its forward movement, when pusher 45 has thrust cam 44 into position A. On the forward movmeent if the press in the direction of arrow 48, limit switch moves with the press the acceleration stretch 49 before it is actuated by cam 44, which emits the impulse for the closing of the press. Before the press ends its forward movement, it moves, by means of pusher 46, cam 44 into position B, which position enables cam 44 on the subsequent return stroke of the press to be thrust by pusher 45 to a new position A1 which corresponds to the turning point of this particular stroke, following which the cycle is repeated. When limit switch 47 passes cam 44 at the return movement of the press, of course, no impulse is emitted for the closing of the press.

Other methods of applying the principle of the invention may be employed instead of those explained above. Changes being made in the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

What is claimed is:

1. A method for the continuous pressing of materials, especially those in the form of a continuously progressing, unbroken mat, such as different types of wooden and fibrous sheet materials, which comprises the steps of: conveying the material to be pressed through the press plates of a mobile press, accelerating said press in a forward horizontal direction which corresponds to the direction of progress of the material, synchronizing the speed of the movement of the press with the speed of movement of the material by blocking said acceleration by means of the driving equipment progressing the material, closing the press to compress the material during the synchronized movement, opening the press, breaking said blocking, retarding the press, and driving the press in a backward direction to the starting point of its forward movement in order to enable the operation cycle to be repeated on the succeeding section of the material to be pressed.

2. A method for the continuous pressing of materials, especially those in the form of a continuously progressing, unbroken mat, such as different types of wooden and fibrous sheet materials, which comprises the steps of: conveying the material to be pressed through the press plates of a mobile press, accelerating and driving said press in a forward horizontal direction which corresponds to the direction of progress of the material, closing the press to compress the material during the forward movement,

synchronizing the speed of the forward movement of the press during compression with the speed of movement of the material, opening said press, absorbing kinetic energy from the press during its phase of retardation in an accumulator for use at the subsequent acceleration .phase, and driving the press in a backward direction at a faster speed, to the starting point of its forward movement in order to enable the operation cycle to be repeated on the succeeding section of the material to be pressed.

References Cited UNITED STATES PATENTS 2,051,011 8/1936 Smith 100207 LOUIS O. MAASSEL, Primary Examiner.

Claims (1)

1. A METHOD FOR THE CONTINUOUS PRESSING OF MATERIALS, ESPECIALLY THOSE IN THE FORM OF A CONTINUOUSLY PROGRESSING, UNBROKEN MAT, SUCH AS DIFFERENT TYPES OF WOODEN AND FIBROUS SHEET MATERIALS, WHICH COMPRISES THE STEPS OF: CONVEYING THE MATERIAL TO BE PRESSED THROUGH THE PRESS PLATES OF A MOBILE PRESS, ACCELERATING SAID PRESS IN A FORWARD HORIZONTAL DIRECTION WHICH CORRESPONDS TO THE DIRECTION OF PROGRESS OF THE MATERIAL, SYNCHRONIZING THE SPEED OF THE MOVEMENT OF THE PRESS WITH THE SPEED OF MOVEMENT OF THE MATERIAL BY BLOCKING SAID ACCELERATION BY MEANS OF THE DRIVING EQUIPMENT PROGRESSING THE MATERIAL, CLOSING THE PRESS TO COMPRESS THE MATERIAL DURING THE SYNCHRONIZED MOVEMENT, OPENING THE PRESS, BREAKING SAID BLOCKING, RETARDING THE PRESS, AND DRIVING THE PRESS IN A BACKWARD DIRECTION TO THE STARTING POINT OF ITS FORWARD MOVEMENT IN ORDER TO ENABLE THE OPERATION CYCLE TO BE REPEATED ON THE SUCCEEDING SECTION OF THE MATERIAL TO BE PRESSED.

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