GB2311747A

GB2311747A - Process and plant for the production of pre-stressed concrete products

Info

Publication number: GB2311747A
Application number: GB9607158A
Authority: GB
Inventors: Remo Ghignone; Edoardo Querin
Original assignee: NORDIMPIANTI OTM Srl
Current assignee: NORDIMPIANTI OTM Srl
Priority date: 1996-04-04
Filing date: 1996-04-04
Publication date: 1997-10-08
Also published as: GB9607158D0

Abstract

Pre-stressed concrete products for the construction industry are produced on mobile production beds (2) which move between a plurality of distinct work-stations (3,5,12,18-22,25) to which the said beds are transported in succession to carry out the steps of cleaning, optionally together with application of release agent; wire drawing of reinforcement; moulding by continuous casting; curing; cutting and unloading.

Description

PROCESS AND PLANT FOR THE PRODUCTION OF CONCRETE PRODUCTS The present invention relates to a process and plant for the production of concrete products and in particular for the production of pre-stressed concrete products.

Pre-stressed concrete products are produced at present by the following process: the pre-stressing steel wires are drawn and tensioned on a steel or reinforced concrete production-track which may be 150 metres or longer, and which has been previously cleaned and coated with releasing agent ; the concrete is than moulded (usually without formworks) by a mobile vibro-finishing machine which moves along the length of the track. Once the moulding phase is finished, the track is covered to accelerate the curing of the concrete product. When the product has cured, the single piece is cut by a cutting machine which moves along the track.

This process involves a series of drawbacks. The production time is extended by the need to move the machines in succession along each track, and the process requires a high labour input. Other drawbaks are the absence of dedicated work-stations, e.g. to cut the product.

The Italian Patent No. 01245313, filed 21.06.90, in the name of Immobiliare Centro Nord S.p.A., suggested using a mobile track moving lengthwise on to transfer the product a roller-way in order to cut it there. This solution did not result effetcive and involved a considerable increase in plant costs without a corresponding decrease in production times and costs.

The objective of the present invention is to address the aforementioned problems by means of a process and plant which can produce prefabricated pre-stressed concrete products in reduced time, with less labour, while maintaining the production standards, i.e. optimum curing times and low levels of noise pollution.

According to a preferred aspect of the invention, the products are pre-stressed concrete products, and the mobile beds which comprise the production-tracks according to the invention are fitted with anchorages means or similar devices to maintain the tension in the pre-stressing steel wires until the end of the concrete curing phase.

According to another aspect of the invention, the beds can move sideways with respect to their long axis and the plant is provided with moving means for the lengthwise movement of the beds.

According to another aspect of the invention, the moulding and cutting machines are static and located at the aforementioned moving means for the lengthwise movement of the beds.

According to another aspect of the invention, the means of curing the concrete comprises a fixed oven which can house a plurality of mobile beds.

The present invention has several advantages over the present state of the art. A continuous production cycle is obtained in which a track, or bed, is completed every two hours, for a total of about 300 m2 of product (which can be increased with larger beds).

Maximum production assuming 24-hour day, can reach 3,600 m2 or more, or twice what can be achieved by a traditional plant with a similar covered area. The labour requiremnts are almost compared to the traditional method.

Further advantages are the dramatical reduction of dust and noise pollution levels, because the cutting and pouring machines being static are easily insulated from the rest of the factory.

The invention will now be described in detail with reference to the attached drawings which are of an illustrative and non-limiting nature, in which: - Fig.l is a schematic top-view of a plant according to the invention; - Fig.2 is a transverse section of a track according to the invention; - Fig.3 is a sectioned schematic view of a part of the plant; and - Fig.4 is a sectioned schematic view of the part of the plant where the concrete cures.

As can be seen in Fig.1, the plant 1 according to the present invention comprises a plurality of fixed workstations, between which move a plurality of beds 2, which form the production-traks on which the desired product is produced. The work-stations are laid out in two parallel rows A and B, adjacent to each other, to form a carousel on which the beds 2 move to effect the various steps of production. As will be explained in more detail below, the work-stations of each row are adjacent and parallel to allow the traks to be moved from one work station to another by simply then sideways. The traks are moved from one row of work stations to the next by lengthwise movement of the beds.

In more detail, the plant 1 provides a work-station 3 on which is located a machine 4 which can move along the bed 2 to clean it, apply a layer of releasing agent and drawing the pre-stressing steel wires (not shown).

Said wires are fed as spools 9 from the store 10 to stationary machine 11 which cooperates with mobile machine 4 to draw and cut the pre-stressing wires. Adjacent to and parallel with the work-station 3 is work station 5 where "static" jacts 6 are located, to tension the drawn prestressing wires.

The wires are fixed at one end to anchorages 7 fixed on the bed 2 and are passed through semi-anchorages 8 which are also fixed on bed 2 on its other and are mobile with it. The semi-anchorages 8 are tightened over the steel wires after the latter have been tensioned by the jacks 6.

The following work-station 12 extends lengthwise over the two adjacent rows of work-stations. In this work-station there is a motorized platform 14, running in a pit 13 (figs. 3 and 4), whose function is to transfer the beds arriving on work-station 5 from row A to row B. At work-station 12 there is also a stationary machine 15 for pouring and moulding the concrete misture; the moulding machine 15 receives the concrete from a concrete-mixing plant 16 where the components are mixed. This underlines the advantages of the plant according to the present invention even in regard the feeding the moulding machine; there is no longer any need for the mobile feeding buckets previously used for filling moulding machines on traditional plants. As has been mentioned above, the platform 14 shuttles across work-station 12 to shift the beds from row A to row B and vice-versa. The concrete is moulded during this movement from A to B, and the speed of the platform 14 is set accordingly.

There is a curing-oven 17 downstream (in terms of the movement of the beds) of the work-station 12. In the embodiment shown in Fig.4, this oven covers workstations 12 and 18 - 22: work-station 12 is where the concrete is moulded, work-stations 18, 19 and 20 are where the concrete cures; work-station 21 is where the pre-stressing wires are de-tensioned by the jacks 27 (preferably located outside the curing-oven 17). The work-station 22 is provided with a pit 13' and a moving platform 14' similar to those of work-station 12 which perform the same bed-shuttling function between the rows B and A.

At work-station 22 there is located a stationary cutting machine 23 to one-piece pre-stressed concrete product into a plurality of individual pieces of the required length.

In this case, too, the advantages of the plant according to the present invention are obvious in that the concrete can be cut in a static emplacement which can be insulated against noise and where dust from the cutting operation can be retained.

The bed 2 is moved along work-station 22 from row B to row A, at an intermittent speed that is set to allow to cut the concrete into single pieces during its movement past machine 23.

Once the bed has been brought over to row A, loaded with the cut products, it is moved to work-station 25, which is immediately upstream of work-station 3 (in terms of the movement of the beds). Works-station 25 is provided with a means of unloading the bed, i.e. a means of removing the cut concrete sections from the bed 2.

This means comprises a lifting trolley 24 moving along the work-station 25 and on to a position 26 where the products removed are stacked and stored to await transport to warehouse storage.

Fig.2 shows a mobile bed 2, fitted with wheels 28 to move sideways with respect to its lengthwise axis and carrying two manufactured concrete products 29. The bed has a reinforced concrete base 30, and pre-stressed by cables 30A which sustain and distribute the load and support the anchorages 7 and 8. In this way the bed acts has a self-reacting formworks.

The process is carried out according the following steps.

First, the machine 4 moves along the bed 2 in workstation 3 to clean off the detritus of the previous cutting and to lay down a layer of releasing agent on the bed. The machine 4 is taken to the end of the bed where there are semi-anchorages 8 and adiacent steel wires dispenser 11, to which spools 9 are fed from store 10 using techniques known per se. In this position the steel wires are hooked onto the machine 4, which draws them along the full length of the bed to anchorages means 7 at the opposite ends of the bed, where they are locked manually. The bed, now cleaned and coated with releasing agent, moves from work-station 3 to the next work-station 5. This is effected by pistons 28 located at the side of the beds , which move them from one work station to the next. Preferably, such pistons are upstream of work-station and in row A and upstream of work-station 12 in row B. In this way, the force exerted by the pistons on the beds at workstations 12 and 22 respectively is also transmitted to the adjacent beds.

The pre-stressing wires are tensioned at work-station 5 by the jacks 6 using techniques known in the art and, the anchorages 8 are then locked.

The bed, now ready to receive the concrete misture, is moved on the motorized platform 14 moving in pit 13 and moves from the row A to row B. During this movement, the bed passes under fixed machine 15, which moulds the concrete; as already described, the speed of the platform 14 depends on the product and the concrete misture, i.e. it is controlled according to the requirements of the machine 15. The machine 15 is fed from the mixing plant 16 where the concrete misture is prepared. At the end of the moulding step, the bed is still at work-station 12, but has moved completely across to row B, inside the curing-oven 17. The concrete moulded product cures as the bed moves from work-station 12 to work-stations 18, 19 and 20. Each shift to next work-station corresponds to the arrival of a new bed in row B. The bed is than moved to work-station 21 where the concrete has cured and the pre-stressing cables can be de-tensioned by releasing anchorages means 8. From this position, the bed is moved on the motorized platform 14' of work-station 22. Here the bed is moved lengthwise, symmetrical to the movement in work-station 12 from row B to row A. During this movement, the bed passes through fixed machine 23 which cuts the pre-stressed concrete casting into a plurality of individual pieces of the required length.

Once the bed loaded with the cut products has been brought over to row A, it is moved to work-station 25, where the bed is unloaded i.e. the manufactured products are taken off by lifting-trolley 24 and moved to the stacking area 26 from where the products are transported by techniques already known (e.g. by a forklift) to a warehouse.

The bed 2 is now ready to be moved to work-station 3 to be cleaned and prepared for another cycle of the carousel.

Claims

1. A process for the production of concrete products, comprising the steps of cleaning, wire drawing, moulding, curing, cutting and unloading characterized by the said product being produced on mobile production beds (2) and the said phases being carried out at distinct work-stations (3,5,12,18-22,25) to which the said beds are moved in succession.

2. A process according to Claim 1, wherein the said wire drawing step comprising the tensioning of a plurality of metal pre-stressing wires.

3. A process according to Claim 2, wherein the tension on the said cables is maintained until after the concrete has cured.

4. A process according to any of the preceding Claims, in which a machine is used in one or more of the workstations (3,5,12,18-22,25), wherein in at least one of said work-stations the relevant step in carried out by moving the production bed (2) with respect to the said machine (15,23)

5. A plant for the production of concrete products on at least one production bed (2) using a plurality of means of production comprising a means of cleaning and preparing said bed (2), means of drawings metal wires, a means of moulding, curing and cutting the concrete, and means of unloading the products, characterized by the said means of production being individually located on a plurality of distinct and fixed work stations (3,5,12,18-22,25) and by the said production beds being mobile in succession to the said plurality of workstations.

6. A plant according to Claim 5, comprising means (4, 6, 11) of tensioning a plurality of pre-stressing wires along the said area, a means (7,8) for maintaining the said pre-stressing wires in tension, said means for maintaining the pre-stressing wires in tension being located on the said mobile beds.

7. A plant according to Claims 5 or 6, wherein the said mobile beds comprising a track (2) and a plurality of wheels (28) to move the said tracks sideways with respect to their long axis.

8. A plant according to Claim 7, wherein by at least two of the said work-stations (12, 22) are provided with means (13, 14, 13', 14') for moving the beds (2) in the direction of their long axis.

9. A plant according to one of the Claims 5 to 8, wherein the said work-stations (3,5,12,18-22,25) are laid out in two adjacent rows (A,B), each row comprising two work stations (12,22) provided with means (13, 14, 13', 14') for moving the beds (2) in the direction of their long axis.

10. A plant according to Claims 8 or 9, wherein the said means (15) of moulding the concrete and (23) of cutting the concrete products are fixed and located at the said work-stations (12, 22) provided with a means of moving the beds (2) in the direction of their long axis.

11. A plant according to any of the Claims 5 to 10, wherein the said means of curing the concrete is a static oven (17).

12. A plant for producing pre-stressed concrete products, substantially as herein described with reference to, or with reference to and as illustrated in, the accompanying drawings.

12. A plant according to Claim 11, wherein the said oven (17) is large enough to contain two or more production beds (2).

13. A bed for the production of pre-stressed concrete products, comprising a track (2) and a means (28) of moving sideways.

14. A production bed according to Claim 13, wherein by the said track (2) comprising a base (30) in prestressed concrete (30a).

15. A process for producing concrete products, substantially as herein described with reference to the accompanying drawings.

16. A plant for producing concrete products, substantially as herein described with reference to, or with reference to and as illustrated in, the accompanying drawings.

17. A production bed for producing concrete products, substantially as herein described with reference to, or with reference to and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows 1. A process for the production of pre-stressed concrete products, comprising the steps of cleaning, wire drawing, moulding, curing, cutting and unloading, in which said product is produced on mobile production beds (2) and in which said steps are carried out at distinct work-stations (3, 5, 12, 18-22, 25) to which said beds are moved in succession, characterized by the fact that said wire drawing step comprise the tensioning of a plurality of metal pre-stressing wires, said pre-stressing wires being mantained in tension by means (7, 8) located on said mobile beds.

2. A process according to Claim 1, characterized by the fact that said mobile beds (2) are moved sideways with respect to their lenghtwise axis to reach at least one of the said work-stations.

3. A plant for the production of pre-stressed concrete products on at least one production bed (2) using a plurality of means of production comprising means of cleaning and preparing said bed (2), means of drawing metal wires, means of moulding, curing and cutting the concrete, and means of unloading the products, in which said means of production are individually located on a plurality of distinct and fixed work stations (3, 5, 12, 18-22, 25), and in which said production beds are mobile in succession to the said plurality of work stations, characterized by the fact of comprising means (4, 6 11) of tensioning a plurality of prestressing wires along said beds, and means (7, 8) for mantaining the said pre-stressing wires in tension, said means for mantaining the pre-stressing wires in tension being located on said mobile beds.

4. A plant according to Claim 3, characterized by the fact that said mobile beds comprise a track (2) and a plurality of wheels (28) oriented to move said tracks sideways with respect to their lenghtwise axis.

5. A plant according to Claim 4, characterized by the fact of comprising means (28') to move said beds sideways with respect to their lenghtwise axis, said means (28') being located at the side of said beds.

6. A plant according to Claim 4, characterized by the fact that at least two of said work-stations (12, 22) are provided with means (13, 14 13', 14') for moving the beds (2) in the direction of their long axis.

7. A plant according to one of the Claims from 3 to 6, characterized by the fact that the said work-stations (3, 5, 12, 18-22, 25) are laid out in two adjacent rows (A, B), each row comprising two work-stations (12, 22) provided with means (13, 14, 13', 14') for moving the beds (2) in the direction of their long axis.

8. A plant according to Claims 6 or 7, characterized by the fact that the said means (15) of moulding the concrete and (23) of cutting the concrete products are fixed and located at the said work-stations (12, 22) provided with means of moving the beds (2) in the direction of their tong axis.

9. A plant according to one of the Claims from 3 to 8, characterized by the fact that the said means of curing the concrete is a static oven (17).

10. A plant according to Claim 9, characterized by the fact that the said oven (17) is large enough to contain two or more production beds (2). 11. A process for producing pre-stressed concrete products, substantially as herein described with reference to the accompanying drawings.