GB2163383A - Method and machine for manufacturing bricks of compressed earth - Google Patents

Abstract

The invention provides a method of and apparatus for manufacturing building bricks by agglomerating an earth-based material, involving feeding the material to a chamber of variable volume and compressing the contents of the chamber with a piston by means of a hydraulic jack, the speed of the piston being reduced towards the end of the compression stage.

Description

SPECIFICATION Method and machine for manufacturing bricks of compressed earth.

The present invention relates to the manufacture of compressed earth bricks.

The construction of buildings using blocks of dried earth is traditional in many countries, and in particular in hot countries with a low rainfall. It appears that rather than developing building materials of a different nature for use in building construction, which materials often require cement to be imported on a large scale, granulates to be crushed, etc., it is often preferable to improve on the local traditional techniques.

The present invention provides more particularly a method an a machine for compressing at a relatively very high pressure, that is a pressure which can be reach several tens of bars, an earth-based material that heretofore did not give satisfactory results as far as the manufacture of bricks is concerned.

It has been observed that, for some earth-based materials, the application of a pressure above a predetermined value results in structure irregularities such as a formation of layers, which considerably limits for some countries the possibility of building houses from compressed earth.

The present invention comprises performing compression of such a material by progressively increasing the pressure of said material by displacing a piston, under the action of a hydraulic jack in a known manner per se, and it is characterised in that this displacement is not performed at a constant speed, but in contradistinction by following a low of reduction of speed toward the end of the stroke.

In a first aspect, the present invention provides a method of manufacturing building bricks from an earth-based material, comprising feeding said material in a chamber of variable volume and compressing the contents of said chamber with a piston by means of a hydraulic jack until a predetermined pressure is obtained, wherein the speed of the piston is reduced towards the end of compression.

In a preferred embodiment, the method comprises the steps of: providing a mold in the form of a chamber of variable volume, its bottom comprising a piston and its top being open; placing the open top of the mold beneath a feeder for supplying an earth-based compressible material; lowering the piston to a predetermined position such that the volume of the chamber corresponds to a measured quantity of said material as supplied by gravity feed; displacing the open top of the mold transversely relative to the direction of material flow to a position opposite to a pressure plate; compressing the contents of the chamber against the said pressure plate by means of the said piston, the piston being driven by a hydraulic jack to apply a predetermined pressure to the said contents;; displacing the mold a second time parallel to the plane of the said pressure plate to disengage the said open top from the pressure plate; and using the same jack to raise the piston to eject the product through the said open top.

Advantageously, compression starts a a relatively high speed during a first or initial phase followed by a relatively slow speed during a second or final phase.

This makes it possible to reach very high pressures without irregularities appearing in the structure of the material which will constitute the final brick, and is applicable to a very wide range of different kinds of earth.

It is believed that this reduction in speed favors the evacuation of air held between particles of brick material, and that the air escapes in spite of the particles being brought closer together as a result of the increasing pressure.

Hydraulic jacks of compression machines are usually actuated by a fluid such as oil, provided from a pump, and the pumps used in such machines normally have a constant flow rate, which leads to a displacement of the jack piston at a constant speed.

This invention, from the machine viewpoint, is characterised by the presence of means which, while maintaining the pump as a means for actuating the jack, allow to adjust the speed of displacement of the jack as a function of the law which has been found as the better for the application under consideration.

Such a machine for manufacturing building bricks by agglomerating an earth based material is of the type comprising a chamber of variable volume, feed means for feeding said chamber with said material and a piston capable of compressing the contents of said chamber by means of a hydraulic jack, and it is characterised by the fact that it comprises means for reducing the speed of the piston at the end of the compression stage.

In a preferred embodiment such a machine comprises: a frame; a mold composed of a chamber having side walls that are parallel to a generator direction and a piston which is free to move inside the chamber along the said generator direction under the control of piston actuator means, one end of the chamber being constituted by the said piston and the other end of the chamber comprising an opening of the same section as the chamber; feed means for feeding said chamber with a compressible earth-based material; a compression plate suitable for closing the said opening to enable the piston to compress the material contained in the chamber, the said feed means and the said compression plate being fixed to the said frame of the machine; and means for disengaging the said opening relative to the said plate to enable the compressed product to be removed from the chamber;; the said piston actuator means comprising a pressure driven jack; the mold, including the piston and its actuator means, constituting moving equipment which is movable relative to the frame for successively positioning the mold opening in a first position opposite the said feed means for filling the mold chamber, and then in a second position opposite the said compression plate for compressing the mold fill; and means being provided for turning off the pressure action of the jack prior to moving the said moving equipment from the first position to the second position.

In one embodiment, where the moving equipment is capable of taking up a third position relative to the frame in which third position the said opening is disengaged from the compression plate, and the jack is operative to eject the molded product through the said opening, the machine includes means for releasing the pressure in the mold chamber before moving equipment from the second position to the third position, said pressure being released prior to moving for sufficient time to enable the compressed earth-based material to expand elastically while still restrained by the mold.

In one embodiment, the feed means for feeding the earth based material include a hopper with an Archimedes' screw and a vibrator to facilitate movement of the material to be compressed, the mold chamber being horizontally movable to take up a position beneath the said hopper.

Embodiments of the invention are described by way of example with reference to the accompanying drawings, in which: Figure 1 is a simplified view of a brick-making apparatus in accordance with the invention showing a hydraulic circuit thereof; Figures 2 to 8 are similar views to Figure 1 under various different conditions; Figure 9 is a detailed hydraulic circuit diagram for the apparatus of Figures 1 to 8; Figure 10 is a diagrammatic side view of an installation including a plurality of pressing machines; Figure 11 is a plan view corresponding to Figure 10; Figure 12 is a perspective of a mixer blade; Figure 13 is a front view of an installation including four press stations; Figure 14 is a plan view on a larger scale of a portion of Figure 11; and Figure 15 is a section on a line XV-XV of Figure 13.

Reference is now made to Figures 1 to 8 which are diagrams showing various stages in the operation of the machine showing the means used for automating this operation.

In the condition shown in Figure 1, referred to as stage 0, the mold 1 is opposite the front portion 2 of the press. A position detector of the inductive type 3 co-operates with an index member 4 which is fixed to the vertical rod 5 of the jack 10 to detect that it is fully extended in order to authorize passing to the following stage or stage I.

As it moves, ie. during the 0-I phase, the mold 1 is drawn horizontally by a jack 6. It retracts until it comes under the hopper 7 while the rod 5 of the jack 10 remains extended since the bottom chamber of the jack remains under pressure. When a detector 8 detects an index 9 (Figure 2) mounted on the body of the jack 10, the mold 1 is stopped.

The detector 8 then authorizes passage to the next stage or stage II.

As it passes from stage I to stage II (filling phase Oil), the rod 5 of the jack 10 moves down, thus admitting a determined volume of earth into the mold 1 from the hopper 7. This volume of earth is adjustable by adjusting the position of a detector 11 for detecting the end of the down stroke of the rod by co-operating with an index 12 on the rod (Figure 3). The said detector 11 serves to authorize passage to the next stage, or stage Ill.

As it passes through phase Il-Ill, the mold 1 moves forwards under the press frame 13. An index 14 on the body of the jack 10 co-operates with a position detector 14' (Figure 4) to stop movement of the mold and to authorize passage to the next stage or stage IV.

As it passes through passes III-IV, the rod 5 of the jack 10 compresses the earth in the mold by means of the piston 20. An index 15 moves with the rod and co-operates with a detector 16 when the jack rod is at an intermediate position on its stroke, eg. about half way (Figure 5). The intermediate position may be adjusted by modifying the position of the detector 16. In this intermediate position, the detector controls the hydraulic circuit of the jack 10 in such a manner as to reduce the speed at which the rod of the jack is extended.

The movement of the rod 5 of the jack 10 during the phase lll-lV thus takes place at two speeds : as relatively high speed until the index 15 co-operates with the detector 16, and a relatively slow speed while the indexl5 co-operates with the detector 16.

To this end, the index 15 is in the shape of an elongate shoe whose height is so determined that the slow speed is maintained for a determined fraction of the stroke of the jack.

As can be seen in Figure 9, two pumps 29 and 30 are synchronously driven by a motor 31 and apply oil under pressure from a source 32 to the body of the jack 10. The jack body is fed via two ducts 33 and 34 respectively for extending and retracting the rod of the jack. The distribution of hydraulic fluid in the ducts 33 and 34 can be modified by means of a three position valve 35 in which the three positions 35r, 352 and 353 are controlled by means of two windings 36 and 37. The three positions 35i, 352 and 353 correspond respectively to the rod extending, remaining stationary, and retracting.

Via a duct 38, the pump 30 is in communication with a duct 39 that leads firstly to the duct 33 close to the pump 29 and secondly to the duct 34 close to a return tank 40. On the section of duct 39 lying between the pump 30 and the duct 33 there is a non-return valve 41 while the other section includes an electrically operated valve 42 having two positions 42, and 422 and actuated by a winding 43. In the position 42, the output from the pump 30 is sent to the tank 40, while in the position 422 communication between the duct 39 and the tank 40 is cut so that the output from the pump 30 is added to the output from the pump 29, by passing through the non-return valve 41.

At the beginning of the Ill-IV phase, the winding 36 is excited and the valve 55 is in position 55,, while the winding 43 is not excited and the valve 41 is in the position 422. As a result the duct 33 is supplied by the outlet form both pumps 29 and 30 so that the ensuing extension motion of the jack's rod is fast, or at least relatively fast.

When the index 15 actuates the detector 16, the detector excites the winding 43 of the valve 42, thereby directing the output form the pump 30 to the tank and leaving only the output from the pump 29 feeding the circuit. The danger of backflow and unwanted vacuum is avoided by the nonreturn valve 41. The flow of oil to the jack 10 is thus reduced and the rod thus moves relatively slowly under the drive of the pump 29 only.

During the phase IV-V, the earth is compressed between the piston 20 and a plate 18 which is a part of the press frame. The pressure applied to the earth in the chamber 17 of the mold 1 increases but the speed of the piston 20 at the end of the jack rod is slower than during the preceding phase.

It has been observed that the structure of the material making up the final bricks is free from irregularities. It is believed that this is due, at least for some earth based materials, to improved evacuation of the air which becomes trapped in the earth during compression. Satisfactory results have been obtained in which the speed of the compressing piston during the second or slow portion of the compression is about half the speed used during the first or fast portion. This simply requires that both pumps 29 and 30 should deliver oil at the same rate.

The oil pressure in the hydraulic circuit of the jack 10 increases to a value which depends on the setting of a pressurestat 19 connected to the hydraulic circuit 21. A value of 260 bars has proved satisfactory. When the said value is reached, the contact in the pressurestat 19 powers a handsettable delay circuit 22 and simultaneously turns off the winding 36, thus bringing the valve 35 to its intermediate position 352. As a result the liquid from the pump 29 is directed to the tank 40, and the liquid from the pump 30 is likewise directed to a collecting tank. This stage constitutes the end of compression and the rod ceases to move.

The next phase V-VI is a timing phase under the control of the time delay circuit 22. During this phase, the liquid from both pumps 29 and 30 is directed to the tank 40 and the supply orifices to the jack 10 are likewise in communication with the tank 40.

During this phase, the moving portion of the jack 10, ie. the rod 5 and the piston, is unpowered and drops under its own weight through a distance which is usually about 5 to 10 mm. The position corresponding to stage VI is practically identical to that shown in Figure 6, except that the moving parts of the jack 10 have dropped by the said 5 to 10 mm. The products in the chamber 17 reaches its final volume by means of an elastic phenomenon.

It has been observed that by using a time delay to ensure that the product decompresses while inside the mold, the end product is of uniform size. This may be explained by the fact that the elasticity which remains in the material is allowed to act while the mold remains fully closed. The time delay thus needs to be adjusted to match the water content of the earth-based material being compressed. If prior tests indicate that the compressed product tends to expand, then the mixture is too wet and the time delay needs to be increased to give the material time to stabilize in the mold.

The passage through phase Vl-VII to reach stage VII is under the control of the time delay contact.

This is the second phase in which the moving equipment comprising the mold 1 and the jack 10 is moved forwards. This stroke takes place under the action of the second jack 6. The equipment moves forwards until an index 23 on the body of the jack 10 is detected by a position detector 24, which ten causes the forward motion to stop (Figure 7) and authorizes passage through phase VII VIII to reach stage VIII.

During phase Vil-VIII, the rod 5 of the jack 10 again moves upwardly. The compressed molded product 25 is expelled from the chamber 17. Since the index 15 is still co-operating with the detector 16, the ejection begins slowly. It continues at higher speed once the index 15 is clear of the detector 16. The end of ejection condition is shown in Figure 8.

Once ejection is over, the index 4 co-operates with the detector 3 which authorizes passage to the next stage which is stage I again, the mold is moved backwards and the above-described cycle recommences.

The maximum pressure developed during brick manufacture is fixed as a function of prior test results on any given raw material.

To obtain bricks of the desired height, the initial volume of the chamber 17 is varied by adjusting the position in which the index 12 co-operates with the detector 11. As shown diagrammatically in Figure 3, the flow chamber 26 of brick making material is provided with one or more feed screws 27 of the Archimedes type and/or of external vibrator means 28 to improve downward movement of the earth powder. Filling the chamber 17 under vibration and under pressure supplied by the screw 27 helps to ensure that the resulting bricks are of uniform quality.

Reference is now made to Figures 10 and 11 which relate to an installation comprising a machine of the type described above. The installation comprises a loading hopper 101 with a hinged grating 102. From the hopper, the material passes via a vibrating feeder 105 to a clump cruscher 103 including a cylinder 104.

The crusched produce arrives at the bottom end of a feed belt 106 which conveys it to a buffer hopper 107. An auxiliary hopper 108 is disposed adja cent to the buffer hopper 107 for receiving bags of cement which are ripped open thereby and which feeds the cement to a cement weighing hopper 109. The buffer hopper 107 has an extractor 111 and the earth and the cement are fed to a mixer 112.

The hoppers 107 and 108 and the mixer 112 are parts of a mixing module which further includes a feed pump 113, a water dispensing device for supplying measured quantities of water, a compressor 114, and a control station 115.

The outlet 116 from the mixer 112 which receives earth from the extractor 111 and cement from the weighing hopper 109 is over the bottom end of a pointable conveyor belt 119 whose top end feeds a press apparatus in accordance 122 with the invention. The press hopper advantageously includes a mixer as shown in Figure 12.

The mixer comprises a shaft 51 fitted with radial arms 52 distributed over its length and extending in various angular directions. A diamatrical arm 52 has mixing blades 53, and 532 at its ends. The same is true of further diametrical arms 522 and 522. The ends of the shaft 51 have end scraping arms 54, and 542. A radial arm 55 has a load-distributing V 56 at its end. The earth arrives from the conveyor belt in the middle of the accomon hopper tank for feeding four presses. The V serves to urge the incoming earth to left and to right, with the mixer turning whenever the belt is feeding earth.

The outlet 123 from each press lies over a roller conveyor 124 on which a brick 125 is drawn.

The installation shown in Figures 10 and 11 has four identical presses whose respective outlets are referenced 123.1, 123.2, 123.3 and 123.4. All four are fed with earth from the same conveyor belt 119 which can be swung through an arc by means of a support wheel 126.

A four-press module is shown in Figures 13 to 15. The earth is delivered by a bucket loader. Figure 14 has arrows showing the directions in which the products are moved.

Figure 15 is a diagrammatic view of a press 131 having a hopper 132 mounted on a frame 133 which also supports a gangway 130. The press frame 133 is under the hopper 132. The mold 134 is horizontally dispiaced by a jack 135. A second jack 136 provides the compression. Finished products 137 follow corridors 139 to reach a conveyor 141 having a product stacking device at its end.

The installation also includes a power unit under the control of programmable control means.

Claims (14)

1. A method of manufacturing building bricks from an earth-based material by feeding said material in a chamber of variable volume and compressing the contents with a piston by means of a hydraulic jack until a predetermined pressure is obtained, wherein the speed of the piston is reduced towards the end of compression.

2. A method according to claim 1 comprising: providing an open topped variable volume mold whose bottom face is constituted by a piston; placing the open top of the mold under a feeder for supplying earth-based compressible material; lowering the piston to a predetermined level to gravity load the chamber with a predetermined volume of material; displacing the mold transversely relative to the loading direction until the said opening is closed by a compression plate; driving the piston by means of a pressure-controlled jack to compress the contents of the mold chamber to a predetermined pressure; displacing the mold transversely a second time to disengage the said opening from the compression plate, and raising the said piston by means of the said pressure-controlled jack to eject the compressed-earth product.

3. A method according to claim 1 or 2, wherein the compression initially takes place at a relatively high speed during a first or initial phase, and wherein the compression takes place at a slower speed during a second, or final phase.

4. A method according to claim 3, wherein the speed of the piston during the final phase of compression is substantially half its speed during the initial phase.

5. A method according to claim 1, 2, 3 or 4, wherein, once maximum pressure has been attained, the pressure in the mold is released for a sufficient period of time to ensure that the compressed earth can expand elastically while still constrained by the mold.

6. A machine for manufacturing building bricks by agglomerating an earth-based material, of the type comprising a chamber of variable volume, feed means for feeding said chamber with said material and a piston capable of compressing the contents of said chambers by means of a hydraulic jack, wherein the machine comprises means for reducing the speed of the piston at the end of the compression stage.

7. A machine according to claim 6, which comprises: a frame; a mold composed of a chamber having side walls that are parallel to a generator direction and a piston which is free to move inside the chamber along the said generator direction under the control of piston actuator means, one end of the chamber being constituted by the said piston and the other end of the chamber comprising an opening of the same section as the chamber; feed means for feeding said chamber with a compressible earth-based material; a compressio plate suitable for closing the said opening to enable the piston to compress the material contained in the chamber, the said feed means and the said compression plate being fixed to the said frame of the machine;; and means for disengaging the said opening relative to the said plate to enable the compressed product to be removed from the chamber; the said piston actuator means comprising a pressure driven jack; the mold, including the piston and its actuator means, constituting moving equipment which is movable relative to the frame for successively positioning the mold opening in a first position opposite the said feed means for filling the mold chamber, and then in a second position opposite the said compression plate for compressing the mold fill; and means being provided for turning off the pressure action of the jack prior to moving the said moving equipment from the first position to the second position.

8. A machine according to claim 7, wherein the said moving equipment is also movable to a third position relative to the frame in which the said opening is free from the compression plate and in which the jack is operative to eject the molded product from the chamber via the said opening, the machine including means for releasing the pressure in the mold chamber before moving the moving equipment from the second position to the third position, said pressure being released prior to moving for sufficient time to enable the compressed earth-based material to expand elastically while still restrained by the mold.

9. A machine according to claim 6, 7 or 8, wherein the feed means include a mixing shaft in the flow chamber.

10. A machine according to claim 6, 7, 8 or 9, including a tank for mixing earth with cement, said tank including a mixing shaft fitted with mixer blades and blades for scraping the walls of the tank.

11. A machine according to claim 6, 7, 8, 9 or 10, wherein the feed means include a feed chamber having a vibrator fitted to its wall.

12. A machine according to claim 6, 7, 8, 9, 10 or 11, wherein the various phases of operation are controlled by induction based position detectors that co-operate with indexes.

13. A method of manufacturing building bricks from an earth-based material, substantially as hereinbefore described with reference to the accompanying drawings.

14. A machine for manufacturing building bricks by agglomerating an earth-based material, such machine being substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.