HRP920439A2 - Method and means for forming blocks from concrete mixture at a high production rate and with high shape definition, and the product obtained - Google Patents

Description

This invention relates to a process and a device for shaping concrete mix blocks, and especially blocks used as an inert mass in household electrical appliances.

As is known, considerable hardness, low price, high specific mass, as well as the ease with which complex shapes can be formed, means that cement and its agglomerates are increasingly used for purposes other than construction, starting from decorative cobblestones to materials for facades, and from statues to products for mechanical use. Of the latter, those used to provide inert mass are of particular importance. In this regard, the obvious need to design constructions that are both functional and strong, while simultaneously using minimal amounts of expensive materials, often makes it necessary to "weight" these constructions with other, cheap materials that will provide an inert function. Typical examples of this type are the constructions of washing machines and household dishwashing machines. Washing machines require a tub that has a significant inert mass to accommodate the rotating drum in order to ensure the stability of the structure, taking into account the vibrations caused by the rotation of an unbalanced mass (represented by the drum when there is laundry in it, especially during spinning). Dishwashers must be weighted to prevent them from moving when the door is opened or the basket of dishes is removed.

In these and other mechanical applications where cement is used (usually together with iron and barite minerals to increase the specific mass, or density) the blocks usually need to be fixed with screws or pre-set reference elements, which require dimensional tolerances that are difficult to achieve. This is because the usual procedures for making such blocks give irregular shapes, not only in terms of the level of surface treatment, but also in terms of dimensions.

One of the most used procedures for their creation includes the following stages:

- extensive filling of the basic half of the mold, metal structure, with a concrete mixture with rounded gravel or crushed stone,

- the use of one blade to remove excess mixture that extends over the leading edges along which the blade slides,

- compaction of the concrete mixture with the other part of the mold,

- subjecting the system to a short degree of vibration in order to compact the mixture,

- separation of the second part of the mold,

- transferring the casting to one belt conveyor, whose belt moves gently through the steam treatment tunnel in order to accelerate the solidification of the concrete.

This common process produces blocks with a very rough surface, due to the use of sand and because the concrete mix is dry, which is necessary not only to achieve low cost, but also brittleness to facilitate removal from the mold.

This surface roughness is further increased by the fact that the particles of the poured mixture remain attached to the mold and thus separate from the poured block.

This common process therefore produces blocks without a properly machined surface, leading to very wide dimensional tolerances for the above reasons, which are therefore hardly suitable for combination with machined mechanical or metal parts of typically high precision.

This process usually leads to very low productivity with correspondingly high costs, as each individual block must be machined by a worker and processed on a vibrating mold machine.

This property of the process usually makes it necessary to shorten the compaction time by vibration of the mixture in the mold, which leads to a concrete block of poor quality.

The poor quality of the blocks produced in this way is also determined by the existence of sharp edges at the place of the composition of the mold halves, which continuously increase due to the sudden wear of the mold along the line of the connection of the mold halves, and which can cause difficulties during handling because they can injure the hands of the worker who handles the blocks ( for example during their installation and during repairs of the obtained household electrical appliances).

One goal of the invention is to provide a process and device for making concrete blocks that will ensure higher productivity than conventional processes.

The next goal is to provide a process and device that will enable the production of blocks with high dimensional accuracy.

The next goal is to achieve concrete blocks, especially for use as inert mass for mechanical applications (washing machines, dishwashers, etc.), which will be very economical.

These and other objectives have been achieved, as will be seen after reading the following detailed description of a process and apparatus for making concrete blocks, with high productivity and with a very well-defined shape, by using a number of plastic molds with recesses, each corresponding to a of two halves into which the block can be divided, which are made on both outer flat surfaces of the mold, so that one mold line can be formed where two adjacent molds will form the cavity to be filled, this line having one upper surface which includes the pouring holes and on which the concrete mixture can be poured to fill the mold cavities. This filling is accelerated by vibrating the line of the mold in order to compact and delaminate with the usual vibrators, placed on the lower longitudinal elements intended for supporting the mold assembly.

The invention will be shown, in the form of examples without limitation, in the attached drawings, where:

figure 1 shows a side projection of the block production plant, with the side walls of the mold filling frame removed,

Figure 2 shows the perspective view of parts of the plant,

Figure 3 represents a cross-section through one mold and shows the shaping of a concrete block with the participation of adjacent halves of the mold,

Figure 4 represents a perspective view of a mold supported on two longitudinal elements,

Fig. 5 shows, in perspective, a section of the filling funnel, resting on the mold line.

According to Figure 1, the stationary frame 1 has feet 1A for resting on the floor 2. This stationary frame has longitudinal elements 1B and vertical columns 1C, 1C'.

It is desirable that there are two longitudinal elements, in order to form a track 1B', 1B" (figure 2) on which the molds 3 can safely rest. Each of these molds consists of two halves 3A and 3B (figures 2, 4) connected to each other with screws 4, possibly over strips 5 for stiffening.

The halves 3A and 3B are connected at their lower part by load-bearing fittings 6A and 6B, made of steel L-profiles. These fittings have outlets 6b' and 6B" whose purpose is to prevent the transverse movement of the mold halves by being placed between two longitudinal elements IB' and 1B". These halves are made of a non-stick plastic material such as polyethylene, polypropylene, or other known equivalent materials. The halves can also be made of a plastic material that is not necessarily non-stick, but instead coated on the surface with some adhesive material such as polyethylene terephthalate (PTFE).

One convenient feature of these plastic mold halves is that they can be molded under pressure, i.e. injection. This means that they can be of small thickness, that they can be combined with stiffening ribs, and that they have specially shaped parts 8A, 8B, which form a convenient attachment or place for mechanical inserts 7 that also have a strengthening function. With the parts 8A and 8B of the mold halves thus shaped, certain parts of the inserts 7 can become accessible from the outside of the block in order to be attached to some structure with screws or the like, certainly after the block with its inserts has been removed from its mold.

This can be seen in Figure 3, which shows an ideal concrete block in the form of an irregular ring, the "hole" of which is formed by two profiled parts 8A and 8B, which have flat ends facing each other, to fit firmly on the insert placed between them. When the half-piece 3A is separated from the half-piece 3B (shown on the left), part of the metal insert 7, which was previously covered by the profiled parts 8A and 8B, is now outside the block and thus accessible for use, for example, to accept fastening screws to the structure of the corresponding machine.

By the process described, the metal inserts are very easily placed and/or held, not only by centering or placing them on the usual pins in the mold half 3B, but also by means of magnets 27 inserted in the rear part of the recess to hold the iron insert before it is finally secured by the action of the adjacent mold 3A .

The halves 3A and 3B are connected by screws 4 or by some other means, including welding, so as to form a mold (Fig. 4) which has two half recesses 9A and 9B which shape the shape of the given concrete block after joining with the second mold. This is clear from figure 3, which shows the mold 3A-3B' in contact with the half of the mold 3B to form the annular concrete block 10. This mold is made of two different halves 3A, 3B' interconnected by screws 4. The front and back surface of the mold 3 they can be designed to be connected to the corresponding back and front surfaces of other molds 3 by means of special connecting elements or by simply engaging the pins 11 in the holes 12.

This coupling operation is performed in such a way that not only the parts are properly hermetically joined and prevent the formation of a sharp edge along their joint line, but also the centering or coaxiality between the molds is ensured, so that the shape they form is correct, and in addition they mechanically stiffen, so that they maintain a group of aligned molds against movement in the transverse direction.

According to Figure 1, the molds 3 are supported (possibly via their fittings 6A and 6B from Figure 4) on the longitudinal elements 1B' and 1B", and move towards each other until they come into mutual contact, so as to form a very long series of molds. This row or line 13 of molds can have on both sides of another parallel line 13 molds 3, so that there can be up to several thousand molds (only one row is shown in the drawings).

In principle, there is no limit to their number. However, for practical reasons, this number is limited by the need to butt-join the individual longitudinal elements 1B and other longitudinal parts of the structure 1, as well as the time required to remove the concrete blocks from their molds, which must certainly be compatible with production needs, certain other operational requirements (such as the number of work shifts).

Each of the rows of molds rests over the end half of the mold 3 on the first stationary stop 14A.

In this way, a single pressure plate 15 can compress the entire string 13 to keep all molds in tight, sealing contact. The pressure plate is initially moved by the hydraulic pressure cylinder, after which, when the position of maximum contact between the molds 3 is reached, the spacers 17A, 17B are inserted between the second stationary stop 14B and the pressure plate 15, in order to maintain the position of maximum contact initially reached by means of the hydraulic cylinder 16.

The hydraulic cylinder 16, which rests on or is attached to the stationary structure 1, for example via another stationary stop 14B, is now withdrawn. Figure 1 shows it in its retracted position.

At this point in the production cycle, a rectangular frame with seals 20 at the lower end is placed on the surface 18 formed by the upper surfaces of the mold 3. This frame forms a receiving space around a series of holes or slots 21 made in the upper surfaces of the mold 3, which are connected with a cavity for the block to be cast. Usually, the section between the holes and the surface 18 is represented by one flat surface on the block when it is removed from the mold.

In this regard, these holes in principle represent the pouring channels of the mold, but such a channel is so short that it is represented by only one flattened surface on the casting. The concrete mixture Z is poured into the parallelepiped frame 18, 19 and flows through the individual holes 21 into the individual mold cavities to fill them. This filling is accelerated by scraping using hand or mechanical scrapers to move the concrete mix so that the holes receive that concrete mix that rests on the remaining flat top surface of the module.

As an alternative to this process of filling the mold cavities with the use of a parallelopiped frame, a funnel-shaped frame 22 is used, supported via a seal 23 on several molds 3D, and along the ends of the slot 21A (Figure 5).

The funnel 22 can slide along the row of molds, so that it also performs the above-mentioned scraping function, especially if the funnel is made with transverse sheet metal guides 24 that are used to strengthen the funnel.

The penetration of the concrete mix Z into the molds will be facilitated by vibrating the molds so that, depending on the actual filling procedure applied, manual or automatic, the filling stage will also include continuous or intermittent vibrations.

The longitudinal sliding of the hopper 22 in the direction of arrows F also represents an advantage, namely, it can move along the row of molds until the concrete mixture contained in the hopper is completely consumed. In this regard, with this type of production it is difficult to prepare the exact amount of concrete mix, so it is recommended to use a number of molds greater than the number of molds that can actually be filled, and then fill them "one by one" while does not consume the concrete mix.

The term "one at a time" is used only to indicate the gradual filling of a series of molds. In fact, whether a parallelepiped frame or a hopper is used, the molds are simultaneously filled in very large groups, which can cover almost all of them. This is what happens, for example, in the case of a parallelepiped frame, where the poured concrete mix Z instantly penetrates through all the slots 21 it encounters. To prevent the molds from being only partially filled, thick blocks 25 of polystyrene foam (or other equivalent material) are placed inside the frame 19, to cover up to the slits 21 and act as a closure.

When the molds (those on the right in Figure 2) with open slots 21 are filled and it is determined that more concrete mixture Z is available, it is consumed by opening the next slots 21 (in the direction of the line of adjacent molds) by removing the blocks 25B, 25A, which cover them. After that, the frame 19 is raised by the usual devices which can be, as shown in the drawing, hydraulic cylinders 28 that engage with the guiding vertical columns, and the usual fuses that protect against falling.

In the case of a sliding funnel (Figure 5), this procedure with blocks is useless, because the same result is achieved by sliding the funnel in direction F along the line of the mold while there is still concrete mix in it. When the molds 3 are filled, with or without vibrations, and with or without "excess" material above the slots, the concrete mixture in the molds settles, or is compacted. This is done by vibrating the direction 13 of the mold for a duration of between 3 and 5 minutes, by vertically vibrating the longitudinal elements 1B (IB', 1B") on which the mold assembly rests. This vibration is achieved by the usual vibrators 26, which work according to the known and used today procedures for regulating the amplitude and frequency to the required acceleration values. The purpose of this vibration is not only to compact, but also to define the condition of the surface of the casting being formed. In this regard, the concrete mix, for example, is composed of about 40% water, 16% cement, while the rest are solid materials of a certain size, such as small pebbles that are usually found in river sand, iron slag, or other minerals of high specific mass (barite) that are usually used in this type of inert block production.

During the vibration of each of the molds 3, those particles of greater mass P (pebbles) acquire greater kinetic energy, which makes them withdraw from the surface of the casting being formed and move towards its interior. As a result, the material with the smallest particle size and specific mass (density) remains on the outside of the block in contact with its surface. In this specific case, this material consists of a combination of water and cement, forming a so-called cement slurry. When the vibration is finished, the concrete block made in this way is allowed to solidify. When removed from its mold, the block will be extremely smooth and precisely shaped, and in addition will have greater chemical resistance and mechanical strength, which is a consequence of the concentration on the periphery, or surface, of a soft material (cement) of very low porosity. In order to remove the blocks 10 from their molds, it is only necessary to release the abutments 17A, 17B from their usual fastening elements (screws, wedges), or to move the pressure plate 15 connected to them. In this way, the individual molds are axially spaced from each other, ready for manual extraction of the blocks molded in them. This extraction is facilitated by the extremely smooth surface of the mold cavity, as well as the non-stick properties of the plastic material used to make the mold, and is further facilitated by the use of common concrete release agents, the most economical of which include diesel oil and vegetable oil blends, paraffins and waxy materials, and which are applied by spraying on the open mold before pouring the concrete mixture into it. This production process can, of course, also use concrete mixes with thinning agents added in the usual way. One example of these is the product known commercially as FLUIMENT 40.

Claims (13)

1. A process indicated by the fact that it includes: - combining in a group a series of molds, at least part of which has in its two outer working surfaces depressions, each of which corresponds to one of the halves into which the concrete block being produced can be divided, whereby this group is formed one upper outer surface in which the mold openings are shaped as pouring channels, - pouring the concrete mixture into the molds, - vibrating the group at least during the pouring of the concrete mixture. 2. The procedure according to the previous request, indicated by the fact that the vibration of the mold is carried out at the frequency and amplitude usual for the area of concrete, and for a time of, for example, between three and ten minutes, whereby this vibration is achieved by the usual devices (26) that act on the longitudinal elements (1B, 1B', 1B") on which the molds rest. 3. The method according to the preceding claims, indicated by the fact that each of the open molds (3) is formed from two halves (3A, 3B) of plastic material with non-stick properties, such as polyethylene (PE), polyethylene terephthalate (PTF) or acrylonitrile butadiene-styrene (ABS). 4. The method according to the previous claims, characterized by the fact that the molds (3) are filled by forming on that upper surface (18), which has slits (21) for filling, a frame for holding the concrete mixture with which the molds will be filled. 5. Device for carrying out the procedure, characterized by the fact that it includes: a) molds made on their two outer sides with recesses corresponding to one of the two halves into which the concrete block being made can be divided, and which are further equipped with pouring channels, in addition, these molds have at least one further flat surface which is longitudinal to the surfaces made with depressions, and with which at least one pouring channel is connected, b) a device for combining a number of these molds to form a single group, as well as means for supporting this group ,c) a vibrator connected to the mentioned means of support in order to transmit vibrations to the mentioned group, d) a device for pouring the concrete mixture, ie) a device that is placed on the group to define the pouring area. 6. The device according to claim 5, characterized in that the molds are equipped with magnetic elements (27) inserted in their rear part to hold the iron inserts (7) in the concrete block (10). 7. Device according to claim 6, characterized in that the device for holding the concrete mixture (Z) is formed from a frame (19) which is equipped, preferably, with rubber seals (20) in order to keep the liquid part of the concrete mixture (Z) in its interior, and which is placed externally around the slot (21) for pouring. 8. Device according to claim 7, characterized in that it has an outer frame (19) which can be vertically raised and fixed in its raised position in a conventional manner. 9. Device according to the previous requirements, indicated by the fact that the device for holding the concrete mixture (Z) is a funnel shaped with a rectangular opening for discharge, the dimensions of which are equal to the width of the slot (Figure 5). 10. Device according to the preceding claims, characterized in that the device for holding the concrete mixture (Z) is sealingly and slidingly movable along the upper surface (18) formed by a row (13) of molds (3), for successive filling of the mold as long as the contained concrete mixture does not completely consume. 11. Device according to claim 6, characterized in that the device for holding the concrete mixture additionally contains movable blocks (25A, 25B) made of foamed polystyrene to cover and possibly reveal the slots (21) of those molds (3) for which the possibility of only partial filling should be avoided . 12. Device according to the preceding claims, characterized in that an agent for thinning the concrete mixture is added to the concrete mixture according to common good practice. 13. Product or block formed from a concrete mixture using the production process according to the previous requirements.