HK1016925B - Method and apparatus for forming a concrete block - Google Patents

Description

Method and apparatus for making concrete blocks

Technical Field

The present invention relates to a method and apparatus for making a concrete block, particularly (but not exclusively) a structural block having a base and reflective facings.

The term "block" as used throughout the specification and claims refers to, for example, a street curb, road divider, and paving stone or similar substrate made wholly or partially of concrete.

Technical Field

A structural block is disclosed in GB 2159556A. The block includes a base and a reflective surface finish and is made by placing a base mix and reflective surface finish mix in a mold and pressing to remove excess moisture.

Another concrete block in the form of a curb is disclosed in GB 2200936. The curbs contain reflective material and are made by mixing the reflective material with the fluid concrete at will, or by compressing the material into the concrete as the curbs partially cure.

Both known concrete blocks are made by a wet casting technique and it takes a considerable period of time, e.g. three days, to cure the block.

Disclosure of Invention

The object of the present invention is to provide a method and a device for making blocks, which can use a dry casting technique. To my knowledge, the reason why dry casting technology has never been used for rimstones is that: it is believed that dry casting techniques can lead to poor strength and durability of the blocks, and the british standard BS7263 published by the british standards association of london: part 1: in 1990 it is stated that a wet casting process is required to meet the requirements of the kerb. However, dry casting techniques may be used in conjunction with a compaction step, so that the resulting block is able to meet the BS 6717: part 1: 1993.

According to the present invention there is provided a dry casting method of making a concrete block comprising the steps of: preparing a base mix having a water/cement ratio less than or substantially equal to 0.35; pouring the base mix into a mold and pressing the mix by applying a vibratory force; wherein, prior to applying a compaction force, a facing mixture is poured into the mold such that the base mixture and the facing mixture are simultaneously compressed; and prior to applying the compaction force, compacting the base mix to form a recess comprised of the base mix and the mold, and pouring the topping mix into the recess.

Preferably, the method further comprises placing a binder between the base mix and the facer mix prior to the compacting step.

Preferably, the facing mixture includes a reflective material.

Preferably, a reflective material is placed on the surface of the facing mixture prior to compaction.

Preferably, the base mix is subjected to a vibratory action to fill the mould and enhance subsequent compaction prior to application of the compaction force.

Preferably, the step of prefabricating the base mix includes mixing cement with granite chips having a diameter of no more than 9 mm and sand particles having a diameter of no more than 5 mm to enhance the cohesive properties of the block.

According to the present invention, there is also provided an apparatus for making a concrete block according to the method described above, comprising: a mixing device for mixing a base mix and a facer mix; a mold assembly comprising a mold and a feed assembly for receiving the base mix and the topping mix and feeding the base mix and the topping mix into the mold; and a ram device for applying a compaction force to the mixture held in the mold.

Preferably the mould means includes a vibration means for vibrating the mould to enhance subsequent compaction.

Preferably, the rammer device is used to apply a vibro-compaction force.

Preferably, the feeding device comprises two portions holding the base mixture and the facing mixture respectively, the feeding device being arranged so that the two portions are located on opposite sides of the mould and are alternately moved over the mould to respectively dispense the base mixture and the facing mixture in the mould.

Drawings

The present invention will now be described more fully hereinafter, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a mixing device;

FIG. 2 is a perspective view of a mold apparatus;

FIG. 3a is an isometric view of a structural block;

FIG. 3b is a side view of the block of FIG. 3 a;

FIG. 3c is a plan view of the block shown in FIGS. 3a and 3 b; and

figure 4 is a perspective view showing a part of an apparatus for the batch treatment of blocks made according to the invention.

Detailed Description

In fig. 1, a mixing device is shown, with a conveying device 2 for conveying the component materials into the mixing device.

The conveyor 2 comprises a plurality of hoppers 3 to 7 arranged to dispense ingredient material onto a main conveyor 8, the conveyor 8 conveying the material into a skip 9. The skip 9 is itself arranged to move along a track 10 which allows the skip to reach its top end 11 to discharge material into an input hopper 12 of the mixing apparatus 1. The raw material in the hopper is either conveyed to a first mixing device 13 for the base mix or to a second mixing device 14 for the topping mix.

In one mode of production, the hoppers 2, 3 and 5 are filled with granite chips, mineral sand and fine sand, respectively. Hopper 6 may contain silica sand and hopper 7 may contain glass beads. The ingredient raw materials for the base mix can then be obtained by dosing predetermined amounts of crumbs and sand from the hoppers 3 to 5 and transferring them by means of the transfer device 8 and the skip 9 into the mixing device 13 for the base mix. The ingredient raw materials for the topping mix may also be similarly dosed in predetermined amounts from the hoppers 5 to 7 and fed into the mixing device 14 for the topping mix.

The base mix preferably comprises the following ingredients:

name of raw materials Number of

20% sand and filler by weight of ordinary cement

Fine sand 0.1-3 mm 08%

60% of sand with the grain size of 0.4-0.5 mm

Granite scrap of 5-9 mm 32%

2-3% of additive cement by weight

Water/cement ratio 30 kg

The facing mixture preferably includes the following components, including a reflective component for forming a composite layer of no less than 8 mm on the block:

name of raw materials Number of

50 percent of silica sand

Fine sand of 0.1-3 mm 10%

White crumb 10%

30 percent of white cement

5-7% of white pigment (titanium dioxide) cement weight

Or 7-9% of yellow pigment cement by weight

Or 5-7% of red pigment cement by weight

20-35 percent of the total mixture of the 250-800 micron glass balls

5% of additive or binder cement by weight

Water/cement ratio 30 kg (0.28-0.35)

The cement, water and other ingredient materials not supplied from the hoppers 3 to 7 may be directly added to the mixing apparatus by automation or manually.

The operation of the delivery device and the mixing device preferably produces alternately a base mix or a topping mix. When the mixing of the base mix or the topping mix is complete, the resultant mix is discharged into a bucket elevator 15 for movement between the outlet of the mixing apparatus (not shown) and the die apparatus 20 shown in fig. 2. As an alternative to the bucket elevator, a belt conveyor may be used instead, or the mixing device may be arranged to discharge the mixture directly into the mould device.

The mold apparatus 20 includes a feed mechanism 21, a ram apparatus 22, and a mold 23. The feed mechanism 21 comprises two feed hoppers 24, 25 located either side of a hydraulic drive ram 26 of the ram device 22 which is located above the mould 23. The feed mechanism also includes a tray portion 27, 28 located below each hopper 24, 25. The tray sections are interconnected by hinge arms 30, 31 to a frame 29 of the mould apparatus 20 to enable the tray sections 27, 28 to be slid from a discharge position above the mould to a transverse position below the respective hoppers 24, 25.

In operation, the bucket elevator 15 moves from the mixing device 1 to the die device 20 and is positioned above the feed hopper 24 or 25 depending on the mixture being loaded by the bucket elevator. A gate mechanism 26 is driven at the bottom of the bucket elevator to discharge the mixture into each hopper. The mixture is then dispensed onto the relevant tray portion 27, 28, which is then slid onto the mould to discharge the mixture into the mould.

The mold apparatus also has a vibratory device (not shown) that is driven to impart vibration to the mold to assist in filling and further compacting the mold. The ram was then lowered into the mold to compact the base mix to some extent to leave a cavity of about 15 mm between the top of the mold and the base mix. The filling process, vibration and initial compaction took about 10 seconds to complete. The hammer head is then raised and the topping mixture, which had previously been discharged into the tray section 28, is placed on top of the base mixture along with the reflective material. Additives and other binders may be placed in the cavity prior to adding the facer mixture, if desired. The ram is lowered again and a vibratory compaction force is applied to compress the base and facing mixture. The hydraulic mechanism of the hammer head is operated to provide simple harmonic oscillations of up to 3,600rpm per second and to exert a maximum compression force of 120 bar on the mass mixture. Filling the mold with the facecoat mixture takes about 4 seconds and the subsequent compaction takes about 4-6 seconds. The die apparatus is thus capable of about five work cycles per minute.

The composite block is demolded in the form shown in fig. 3, and the compacted base thickness 'T' (for example) is about 80 mm, and the facing 33 thickness 'T' is not less than 10 mm. The length of the block 'L' is about 200 mm and the width 'W' is about 100 mm, although the specific profile and block size may vary as desired.

The blocks may be demolded directly onto a pallet 37, as shown in fig. 4, and transferred by transfer means to a rack for transport by forklift for placement in a curing chamber. Curing takes 8 to 12 hours, and the block will then become sufficiently hard for handling and packaging. Packaging is facilitated by transporting the pallet at the bottom of a gripper 38 which grips the blocks together from four opposite sides so that the blocks can be positioned closely at location 39 for bonding and subsequent packaging.

It will be appreciated that the above described mode of operation is described in terms of an automated process. However, any manufacturing steps may be replaced by manual work. Furthermore, the mold and ram can be manufactured to form one block or multiple blocks in a single work cycle. The shape and contour of the block may be user specified so that the device can produce blocks for a number of different purposes. For example, the reflective mass made according to the invention can be used as directional arrows in roads, isolation lines, double yellow or white lines, road boundaries, numerical or verbal signs, border stones or paving stones, and can be made white, yellow or red according to any need. The block may also be made of different reflective materials if desired.

However, the most significant advantages of blocks made using dry casting techniques in combination with compaction techniques are: since it can significantly shorten the curing time compared to the wet casting technique, and can comply with BS 6717: part 1: 1993, the extrusion strength requirement, thereby improving the production speed and efficiency.

Finally, it is to be understood that the inventive concept is capable of many different constructions and that the generic principles defined herein may not be replaced by specific details. The present invention may take on many variations, modifications, and/or other forms of construction without departing from the spirit or scope of the present invention.

Claims (10)

1. A dry casting method for making a concrete block comprising the steps of:

preparing a base mix having a water/cement ratio less than or substantially equal to 0.35;

pouring the base mix into a mold and pressing the mix by applying a vibratory force; it is characterized in that the preparation method is characterized in that,

pouring a facing mixture into the mold such that the base mixture and the facing mixture are simultaneously compressed prior to applying a compaction force; and

prior to applying the compaction force, compacting the base mix to form a recess comprised of the base mix and the mold, and pouring the topping mix into the recess.

2. The method of claim 1, further comprising placing an adhesive between the base mix and the facer mix prior to the compacting step.

3. The method of claim 1 or 2, wherein the facing mixture comprises a reflective material.

4. The method of claim 1 or 2, wherein a reflective material is placed on the surface of the facer mixture prior to compacting.

5. The method of claim 1, wherein the base mix is subjected to a vibratory action to fill the mold and enhance subsequent compaction prior to applying the compaction force.

6. The method of claim 1, wherein the step of preparing the base mix includes mixing cement with granite chips having a diameter of no more than 9 mm and sand particles having a diameter of no more than 5 mm to enhance the cohesive properties of the blocks.

7. An apparatus for forming concrete blocks according to the method of claim 1, comprising:

a mixing device for mixing a base mix and a facer mix;

a mold assembly comprising a mold and a feed assembly for receiving the base mix and the topping mix and feeding the base mix and the topping mix into the mold; and

a ram device for applying a compaction force to the mixture held in the mold.

8. Apparatus according to claim 7, wherein the mould means includes a vibration means for vibrating the mould to enhance subsequent compaction.

9. The apparatus according to claim 7 or 8, wherein the ram means is adapted to apply a vibratory compaction force.

10. The apparatus according to claim 7, characterized in that said feeding device comprises two portions holding said base mixture and said facing mixture, respectively, said feeding device being arranged so that said two portions are located on opposite sides of said mould and are alternately moved above said mould to mix said base mixture and facing mixture, respectively, in said mould.