METHOD AND DEVICE FOR MAKING VIBRATED CONCRETE ELEMENTS

Abstract: Method and device for making vibrated concrete elements, preferably building elements, comprising the steps of mounting a mould on a mould table (1) which in operation is horizontally oriented; arranging reinforcement steel, insulation, cast-in fittings, adjusting members etc. in the mould; filling the mould with concrete; and vibrating the mould table and the mould. A base (4 - 6) supports the mould table and a vibrator is connectible to the mould table (1) and the base (4 - 6). The invention is characterised in that the mould table (1) is vibrated only in the horizontal plane in one or two directions, that the mould table is vibrated in the frequency range that falls below the audible range, and that the mould table is vibrated by means of at least one pair of cooperating hydraulic cylinders (7, 8) which are aligned with one another and attached to the mould table (1) or the base (4 - 6) and which are adapted to releasably engage the base or the mould table, the frequency of vibration being controlled by a control device which is connected to the hydraulic cylinders (7, 8).

Description: METHOD AND DEVICE FOR MAKING VIBRATED CONCRETE ELEMENTS The present invention relates to a method and a device for making vibrated concrete elements, preferably building elements, comprising the steps of mounting a mould on a mould table which in operation is horizontally oriented; arranging reinforcement steel, insulation, cast- in fittings, adjusting members etc. in the mould; filling the mould with concrete; and vibrating the mould table and the mould. A base supports the mould table, and a vibrator is connectible to the mould table and the base. More specifically, the invention relates to the making of insulated facing elements in the size 4x10 m and weighing about 40 t. In the production of vibrated concrete elements, the concrete is usually vibrated in the mould by means of pokers which are immersed manually in the concrete. This method is not only irrational; it is also annoying because of the noise made by the pokers which oscillate at a fre¬ quency of about 10 kHz. It is also prior art to make vibrated concrete ele¬ ments by means of a mould which is attached to a mould table. The table is connected to a vibrator which vibrates the table in the vertical direction. Also in this case an annoying noise is produced since, as a rule, the frequency of oscillation of the vibrator is in the range 6-8 kHz, i.e. well within the audible range. A further drawback of this prior art device is that when making insulated sandwich-type walls and bases, it is frequently difficult to compact the uppermost concrete surface owing to the vibration-damping effect of the intermediate insulating layer. EP-A2-0,183,682 discloses a method for vibrating con- crete. In this method, the mould walls which are in con¬ tact with the fresh concrete, are caused to make a simul¬ taneous and synchronised oscillating motion which causes shearing motions in the fresh concrete. By means of this method, extremely thin concrete structures can be pro¬ duced. The vibration is carried out by means of a camshaft device which is connected to the mould walls. This patent specification thus is directed to the manufacture of lightweight structures and therefore is not applicable to the manufacture of heavy building elements, such as the above-mentioned facing elements. This prior art mechanical vibrator cannot vibrate heavy elements. The object of the present invention is to provide a method and a device for making vibrated concrete elements which can have a high weight and be provided with an em¬ bedded insulation. A further object of the invention is to provide a method and a device which give a concrete element, the concrete being homogeneous and without voids through the entire element in the making of both massive and insulated concrete elements. One more object of the invention is to provide a method and a device for making vibrated concrete elements, by means of which the vibration of the concrete can be ef¬ fected in a comparatively silent manner. A still further object of the invention is to provide a device in accordance with that stated above, which can be applied to most of the existing mould tables that are intended for the production of massive or insulated walls or bases of concrete. Many mould tables are already equip¬ ped with hydraulic cylinders for raising the mould table when lifting out the elements. At a relatively moderate cost, it will be possible to supplement existing hydraulic assemblies with the vibrator according to the present invention. According to the invention, these objects are a- chieved by a method as stated above, which is charac- terised in that said mould table is vibrated but in the horizontal plane in one or two directions, that said moul table is vibrated in the frequency range below the audibl 3 range, and that said mould table is vibrated by means of at least one pair of cooperating hydraulic cylinders, the frequency of vibration being controlled by a control de¬ vice which is connected to the hydraulic cylinders. A device for carrying out the method and as stated above is characterised according to the invention in that the vibrator comprises at least one pair of cooperating hydraulic cylinders, the two hydraulic cylinders included in each pair being aligned with one another and directed towards or away from one another, the pair or pairs of cooperating cylinders being attached to said mould table and adapted to releasably engage said base, or being attached to said base and adapted to releasably engage said mould table, and a control device being connected to each pair of hydraulic cylinders for alternately increas¬ ing the pressure in one hydraulic cylinder and lowering the pressure in the other hydraulic cylinder. Further developments of the invention are evident from the characteristic features stated in the subclaims. Preferred embodiments of the invention will now be described for the purpose of exemplification, with re¬ ference to the accompanying drawing in which Figs 1 - 4 are schematic, perspective views of the device according to the invention, with no mould for better clarity, one pair of cooperating hydraulic cylinders being alterna¬ tively positioned. Fig. 1 shows the hydraulic cylinders attached to the . base and directed towards one another and releasably en¬ gaging the circumferential portion of the mould table, Fig. 2 shows the hydraulic cylinders attached to the circumferential portion of the mould table and directed away from one another and releasably engaging the base, Fig. 3 shows the hydraulic cylinders attached to the base in the area of the central portion of the mould table and releasably engaging the central portion of the mould table, Fig. 4 shows the hydraulic cylinders attached to the central portion of the mould table and releasably engaging the base in the area of the central portion of the mould table, Fig. 5 is a top plan view of an application of the invention, and Fig. 6 is a partial side view illustrating the appli¬ cation of the invention as shown in Fig. 5, the hydraulic cylinders being attached to the mould table and released from the base. In Figs 1 - 4, the unfilled double arrows indicate the mould table direction of vibration in the horizontal plane. The smaller, filled single arrows indicate the direction of motion of the piston rods of the hydraulic cylinders for engaging the mould table and the base, respectively. With reference to Figs 1 - 4, the device according to the invention comprises a mould table 1 having a mount 2, the mould table being movably arranged on the mount, and friction elements 3 being mounted between the mould table and the mount. During operation, the mould table 1 is horizontally oriented and joined with a mould (not shown). The mount 2 is supported by a base 4, preferably a strong concrete floor or the like, in a recess 5 formed in the floor as shown in Figs 1 and 2, or above supporting struc¬ tures 6 of the floor. A pair of hydraulic cylinders 7 and 8 are arranged between the mould table 1 and the base 4. The hydraulic cylinders 7 and 8 are aligned with one another and cooperate so as to cause the mould table to vibrate, as will be explained in detail below. Figs 1 - 4 show only one pair of cooperating hydraulic cylinders 7 and 8, but when required it is of course possible to ar¬ range more than one pair of hydraulic cylinders between the mould table 1 and the base 4. Further the hydraulic cylinders are shown to be oriented in the longitudinal direction of the mould table, but if desired it is of course possible to orient the hydraulic cylinders in the transverse direction of the mould table or in both the longitudinal and transverse direction of the mould table. Reference is now made to Fig. 1, showing the mould table 1 positioned in a recess 5 formed in the base 4. The hydraulic cylinders 7 and 8 are attached to the walls of the recess and are directed towards one another. On actua¬ tion of the hydraulic cylinders, their piston rods are extended in the direction of the filled arrows and are caused to engage the mould table. When the device is not operated, the piston rods are retracted in the hydraulic cylinders and thus released from the mould table. Fig. 2 distinguishes from Fig. 1 only in that the hydraulic cylinders 7 and 8 are attached to the mould table and directed away from one another, i.e. towards the recess walls which they are caused to engage during opera¬ tion, as the piston rods are extended in the direction of the arrows. Fig. 3 illustrates the hydraulic cylinders 7 and 8 attached to supporting structures 6 of the base 4 and di- rected towards one another and towards a mould table por¬ tion 9 which projects downwardly. During operation, the piston rods are extended in the direction of the arrows and are caused to engage the projecting portion 9. When the device is not operated, the piston rods are retracted in the hydraulic cylinders and thus released from the mould table. Fig. 4 differs from Fig. 3 only in that the hydraulic cylinders 7 and 8 are attached to the projecting portion 9 of the mould table 1 and directed away from one another, i.e. towards the base supporting structures 6 which they are caused to engage during operation, as the piston rods are extended in the direction of the arrows. When making vibrated concrete elements, preferably flat building elements having a large surface, the mould is attached to the mould table the size of which can be 4x8 m. Subsequently, reinforcement steel, insulation, cast-in fittings, and adjusting members for windows and other openings are arranged in the mould and on the hori¬ zontal mould table, whereupon the mould is filled with concrete. The vibration of the mould table and the mould is ef- fected by causing the hydraulic cylinders to engage the mould table and the base, respectively, as described a- bove. The pair or pairs of cooperating hydraulic cylinders 7 and 8 are connected to a control device (not shown), a given pressure prevailing in the hydraulic cylinders. The mould table is caused to move in that hydraulic oil is pumped at a predetermined pressure and flow to the hydrau¬ lic cylinders via reversing valves included in the control device, such as on-off valves, proportioning valves or servo valves, depending on the required swiftness of the shifting operation. The solenoids of the reversing valves are shifted electronically and, thus, also the motions of the mould table are changed electronically, e.g. by means of a potentiometer. The amplitude and frequency of the mould table are changed, preferably by adjustment of the time (electronically), the pressure and/or flow (hy- draulically). Thus, the mould table is vibrated by alternately in¬ creasing the pressure in one hydraulic cylinder and lower¬ ing the pressure in the other hydraulic cylinder. The frequency and amplitude of the vibration are selected by the control device. A preferred frequency is in the range 0.5 - 5 Hz, i.e. far below the range audible to human beings. In testing, the optimal frequency has been found to be in the range 0.5 - 7.0 Hz, i.e. in the size of 100 - 400 strokes a minute for the hydraulic cylinders. The preferred amplitude is about ± 10 mm. Reference is now made to Figs 5 and 6 which are a top plan view and a partial side view of an application of the present invention. In Fig. 5, the mould table 1 as well as its longitudinal beams 10 and the mount 2 are indicated by dash-dot lines. The mould table 1 is pivoted to the mount 2 by hinge means 11 permitting mould table motions in the horizontal plane in relation to the mount 2 which is fixedly attached to the base 4. By means of hydraulic cylinders 12, the mould table can be pivoted about the hinge means 11 to a raised position for stripping the finished concrete element or to be serviced. The hydraulic cylinders 12 are connected both to the mould table 1 and to the mount 2 and, like the hinge means 11, permit mould table motions in relation to the mount. A substantially U-shaped supporting structure 6 is attached to the base 4 by bolt joints 13. Moreover, the supporting structure 6 is, via inclined beams 14, fixedly connected to the mount 2. The supporting structure 6 is generally designed as a box girder with end walls 15 ex¬ tending above the box girder, see especially Fig. 6. In the illustrated application of the invention, the hydraulic cylinders 7 and 8 are attached to the mould table projecting portion 9 and directed away from one another, as schematically shown in Fig. 4. In Fig. 6 (how¬ ever, not in Fig. 5), the projecting portion 9 is indi- cated by dash-dot lines, but in this Figure the mould table has been left out for better clarity. During opera¬ tion, the piston rods of the hydraulic cylinders 7 and 8 are extended away from the projecting portion 9 and en¬ gaged with the end walls 15 of the supporting structure 6, whereupon the mould table is vibrated in its longitudinal direction, as described above. This means that the mould table slides on coacting pairs of the friction elements 3, one friction element in each pair being mounted on the mould table lower side and the other one on the mount 2 (not shown in Figs 5 and 6). Suitably, one friction ele¬ ment is convex in cross-section and the other friction element complementarily concave in cross-section so that the friction elements jointly form a guide for the motions of the mould table. The structure according to the present invention as shown in Figs 5 and 6 can, as is obvious to a person skil¬ led in the art in the light of what has been stated above, be applied to new constructions as well as to most ex¬ isting mould tables for making vibrated concrete elements. As is also apparent from the application shown, the hy¬ draulic cylinders 7 and 8 of the vibrator can be asymmet- rically arranged in relation to the mould table. The present invention has been described to be particularly advantageous in the making of insulated concrete elements since the concrete is homogeneous and without voids throughout the concrete element. Of course, the invention is also advantageous when making massive concrete elements, inter alia owing to the comparatively low sound level in operation. The invention is not restricted to that described above and shown in the drawing but may be modified in various ways within the scope of the appended claims.

Claims: CLAIMS 1. A method for making vibrated concrete elements, preferably building elements, comprising the steps of mounting a mould on a mould table which in operation is horizontally oriented; arranging reinforcement steel, in¬ sulation, cast-in fittings, adjusting members etc. in the mould; filling the mould with concrete; and vibrating the mould table and the mould in the horizontal plane only, c h a r a c t e r i s e d in that said mould table (1) is vibrated horizontally in two directions, the vibration in one direction occurring independently of that in the other direction, that said mould table is vibrated in the fre- quency range that falls below the audible range, that said mould table is vibrated by means of at least two co¬ operating pairs of hydraulic cylinders (7,8), said pairs making an angle with one another, and that the amplitude and the frequency of the vibrations are controlled in- dependently of one another and in each direction of vib¬ ration by means of a control device which is connected to the pairs of hydraulic cylinders. 2. The method as claimed in claim 1, c h a r a c ¬ t e r i s e d in that said mould table is vibrated at a frequency in the range 0.5 - 7 Hz. 3. The method as claimed in claim 2, c h a r a c ¬ t e r i s e d in that said mould table is vibrated at a frequency in the range 1.0 - 2.0 Hz. 4. The method as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that said mould table is vibrated at an amplitude of about ± 10 mm. 5. A device for making vibrated concrete elements, preferably building elements, comprising a mould mounted on a mould table (1) which in operation is horizontally oriented, a base (4 - 6) supporting said mould table (1), and a vibrator which is connectible to said mould table (1) and to said base (4), c h a r a c t e r i s e d in that said vibrator comprises at least two cooperating pairs of hydraulic cylinders (7,8), said pairs making an angle with one another, the two hydraulic cylinders (7,8) included in each pair being aligned with one another and directed towards or away from one another, the pairs of cooperating hydraulic cylinders being attached to said mould table (1) and adapted to releasably engage said base (4 - 6) or being attached to said base (4 - 6) and adapted to releasably engage said mould table (1), and a control device being connected to each pair of hydraulic cylinders (7,8) for controlling the amplitude and frequency of the vibrations independently of one another and in each direc¬ tion of vibration. 6. The device as claimed in claim 5, c h a r a c - t e r i s e d in that the pairs of cooperating hydraulic cylinders (7,8) are arranged in the area of the central portion of said mould table (1) and/or adjacent the cir¬ cumferential portion of said mould table. 7. The device as claimed in claim 5 or 6, c h a r - a c t e r i s e d in that friction elements (3) are mounted between said mould table (1) and the mount (2) thereof which is fixedly attached to said base (4). 8. The device as claimed in any one of claims 5 - 7, c h a r a c t e r i s e d in that said mould table (1) is pivoted to the mount (2) by hinge means (11). 9. The device as claimed in claim 8, c h a r a c ¬ t e r i s e d in that hydraulic cylinders (12) which are movably arranged in one direction of vibration are attached both to said mould table (1) and to said mount (2) for pivoting the mould table and the mould to a raised position.

Inventors: LARSSON KENT, LARSSON, KENT
Applicants: LENNQVIST MEKANISKA VERKSTAD A, AB LENNQVIST MEKANISKA VERKSTAD
Application year: 1990
Main classification: B28B1
IPC codes: B28B1