FI93326C - Device for forming hollow concrete slabs - Google Patents

Description

93326

Device for forming hollow concrete slabs. - Anordning för att bilda hälbetongplattor.

The invention relates to an apparatus for forming hollow concrete slabs, the apparatus comprising a feed cone for supplying concrete or the like by gravity to a feed screw chamber below, a mold chamber downstream of the feed screw chamber, comprising sealing and leveling means for compacting and leveling concrete below the cone, the feed screws comprising main feed screws each having a stationary shaping mandrel and a final tube and a power source for rotating the feed screws, wherein at least one of the feed screws is an auxiliary feed screw having a first upstream portion having a substantially constant diameter and a second downstream portion; the diameter gradually decreases from the end adjacent to the upstream part.

Building regulations in some countries require that the cavities of such tiles be substantially rectangular in cross-section and formed by a conventional cavity forming device, for example, of the type described in U.S. Pat. 3159898, Ellis et al., U.S. Pat. 3284867, Booth, and U.S. Pat. 3781154, Herbert et al. is shown and described.

In recent years, new slabs with thicker dimensions (larger cross-sectional area) have been introduced in hollow technology to provide a slab that extends over longer distances and has a higher load capacity for use in parking garages, large terminals and larger buildings. Building regulations require the slab to be lightweight, but still suitable for longer distances and higher loads.

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Today, there are some extruders that can make 40 cm (16 inch) tiles with four cavities using four conventional feed screws. In this case, the difficulty is that the large area above the conventional feed screws has to be filled with a concrete mixture and pushed over the "hump" of the casting core. Since only a limited amount of mixture can be fed with a conventional feed screw, the concrete tends to protrude back over the feed screw and not over the casting core. This causes a defect at the top of the slab, resulting in poor tightness and lower load capacity.

U.S. Pat. No. 3,605,217 and FI Patent No. 750484 disclose an extruder for making piles. Both presses have feed screws that extend through the feed chamber to ensure a suitable supply of concrete to the extruded piles. The volume of concrete used in connection with piles is considerably larger in relation to the volume of a single hollow core than in the case of hollow core slabs, so there are difficulties with the appropriate volume of concrete to be fed into the mold chamber. It can be seen that these feed screws do not extend into the mold chambers. In U.S. Pat. No. 3,605,217, the mold chamber is below the conveying plate under the vibrating unit, well downstream of the auxiliary feed screw. Correspondingly, the mold chamber in FI publication 750484 is associated with vibrators, clearly downstream of the feed screws.

In FI publication 53411, the feed screw offers to a large extent the same function as the piston described on drawing page 3. The task here is to feed loose concrete into the feed chamber. The feed chamber, where the sealing rollers act on the concrete, is clearly downstream of the feed screw.

According to the invention, there is provided an apparatus characterized in that the sealing and leveling means comprise a conveying plate (known per se), the auxiliary feed screw having a core spindle having a substantially constant diameter at the upstream part and a gradually decreasing diameter at the downstream part; the threaded flange of the auxiliary feed screw has a substantially constant diameter in the upstream portion of the auxiliary feed screw and a decreasing diameter in the downstream portion, adjacent the upstream portion to the outermost end of the core mandrel; and a second, downstream, conical portion of the auxiliary feed screw extends into the mold chamber below the compression plate to act against the concrete compacted by the compression plate in the mold chamber.

In the invention, the auxiliary feed screw extends through the feed zone and into the mold chamber, where it acts on the concrete to be compacted, ensuring an even distribution of concrete throughout the slab. In addition, because the auxiliary feed screw acts toward the mold chamber under the compression plate, it provides a uniform density and thus strength throughout the plate, where sealing by the compression plate alone would leave zones of low density and reduced strength. Further, by acting against the compacted concrete, the auxiliary feed screw provides a thrust in the machine, which force is not present if the feed screw simply feeds the loose concrete to the feed zone upstream of the compaction chamber.

The device may include at least a main feed screw extending below the feed cone and having a stationary shaping mandrel at the outermost end of the main feed screw in the mold chamber, the auxiliary feed screw being located immediately above or on the side of the main feed screw horizontally and parallel thereto. The auxiliary feed screw can fill all possible cavities in the plate.

In a device comprising a plurality of adjacent, parallel main feed screws extending below the feed cone and into the mold chamber and at the outermost end of each main feed screw of the stationary forming mandrel in the mold chamber, the auxiliary feed screw may be located between two adjacent main feed screws. This allows the core to be eliminated in order to meet the 4 93326 specified load criteria. A conventional method of achieving this is to make a number of openings in the slab, being fresh, above a certain core and then to fill the cavity through the openings with a concrete mixture. This cavity then dries and shrinks, usually more than the surrounding slab, because it is not compressed and does not adhere to the surrounding slab material as desired to form a solid body.

By using the auxiliary feed screw at this particular cavity location instead of the conventional feed screw, the cavity at this point in the cavity plate fills and the filled opening becomes integral with the rest of the extruded plate.

If it is desired to produce a solid slab, without any special features of the hollow core slab, all conventional feed screws are removed simultaneously with the casting core and finishing tubes and an auxiliary feed screw is used at each cavity to compact the concrete mix and provide the necessary extrusion effect. Under these conditions, a solid slab is obtained instead of a hollow slab.

The auxiliary feed screws are easy to install and disassemble and attach to the bearing brackets and actuator in the same way as conventional feed screws.

Other preferred embodiments of the invention are set out in the subclaims.

Figure 1 is an end view of the cavity plate and shows the location of the auxiliary feed screw to eliminate one cavity opening.

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Figure 2 is an end view of a slab in which all cavities have been eliminated by placing auxiliary feed screws at each cavity.

Figure 3 is an end view of a relatively large sized plate outlining the locations of conventional cavity forming screws and auxiliary feed screws to fill a wide area above the conventional feed screws.

Figure 4 is a schematic side view of a cavity forming device with the auxiliary feed screws in place.

Figure 5 is a side view of an auxiliary feed screw of the "mounting flange" type.

Figure 6 is a side view of a "straight spindle" type auxiliary feed screw.

Figure 7 is a schematic end view of a conventional feed screw, finishing tube and auxiliary feed screw arranged to form a plate with horizontal, substantially rectangular cavities.

Figure 8 is a schematic plan view from above of Figure 7.

Figure 9 is a partial end view of a portion of the slab with horizontally arranged cavities.

Fig. 10 is an enlargement of Fig. 3 and shows structural details of the present embodiment.

Figure 11 is an end view seen from the right side of Figure 3.

Figure 12 is a schematic end view of the downstream end point of the auxiliary feed screw and illustrates the radially outward direction of concrete provided by the auxiliary feed screw.

In the drawings, the same reference numerals refer to the same parts in different figures.

The invention will now be described in detail with reference to Figure 3, which shows one embodiment of a relatively large cross-sectional slab with a depth of 16 inches or more.

This plate has four hollow longitudinally extending openings 10 which are substantially rectangular as seen from the end view and have substantially vertical sides 11, inclined upper wall portions 12 and a curved upper connecting wall 13.

The bottoms of the cavities comprise a horizontal bottom wall 14 and inclined walls 15 extending from the ends of the bottom 14 to the lower ends of the vertical walls 11. However, these cross-sectional shapes are only exemplary, as is the number of cavities described, namely four pieces.

Slab 16 is formed by a conventional cavity forming apparatus as described in the aforementioned patents and includes a floor 17 on which the slab is formed. The device, schematically described and generally referred to as 18, includes a feed cone 19. The main conventional cavity forming screw 20 (one for each cavity opening) which is rotated by a power supply (shown schematically as

II

7 93326 with reference numeral 20A) and obtains the concrete from the feed cone, compacts the concrete and compresses it behind the device when the device is moved forward along rails (not shown) by the resistance caused by the cavity formed on the floor 17.

A fixed forming tube or casting core 21 is placed at the end 22 of the main feed screw and a fixed finishing tube 23 is placed behind the forming tube to finish the inside of the cavities 10 as the mass is pressed past it.

To provide a cavity shape similar to that shown in Figure 3, for example, the top side of the forming tube has an upwardly sloping, extending surface 24 leading to an upper horizontal surface 25 which may be curved transversely curved to form curved top walls 13 of boreholes or cavities 10.

Due to the increased height of the cavities, the use of a conventional feed screw 20 poses some problems, as this large area must be filled with concrete and then pushed over the hump or the surface 24 up into the area between the baffle plate 26 and the leveling plate 27, forming a finished slab surface 28 and lack of material flow. these areas may cause a deficiency in a certain area, thus making it impossible to continuously compress an acceptable product with the required strength properties. In fact, depression sometimes occurs in the area above the boreholes.

For one purpose of the present invention, this disadvantage is overcome by providing an auxiliary feed screw, generally referred to as 29, located above the conventional feed screw 20 and rotated by a power supply by means of a chain drive or by any other conventional and generally known manner. These auxiliary feed screws are placed one 8 93326 above each conventional feed screw and are supported at their inner ends 30 freely in a conventional manner on bearings (not shown) in front of the wall or shutter plate 31 of the device. These auxiliary feed screws may include a mounting flange 32 as shown in Figures 5 and 10, or may be "straight spindle" type feed screws as shown in Figure 6.

In either case, the front portion 33 of the auxiliary feed screw is provided with a threaded flange 34 surrounding a mandrel 35 having a constant mandrel diameter, and the threaded flange also has a constant diameter and a constant thread pitch.

The rear portion 36 of the auxiliary feed screw has a mandrel that can taper toward its rear end 37 and is provided with a threaded flange 38 as an extension of the threaded flange 34, which also has a constant thread pitch but decreases in diameter toward the end 37.

This is located immediately above the conventional feed screw and below the feed cone 19 and can fill the cavity at the top of the slab and help force it over the forming tube or casting core extending portion 24, providing a uniform concrete tightness and consequently a much stronger slab. A conventional compression plate reinforces and seals the concrete between the plate and the forming pipe, and the leveling plate 27 flattens and finally dimensions the area between the leveling plate and the finishing pipe.

In Figure 1, the auxiliary feed screw 29 is shown in schematic form positioned in place of a conventional feed screw, with the casting core and finishing tube filling the point where the cavity would normally form. In other words, the auxiliary feed screw prevents the formation of a cavity at this point and replaces the cavity with a concrete mix that is part of the overall concrete mix that forms the slab, thus providing a strong concrete mix in this area. The installation method of the auxiliary feed screw is similar to that of the conventional 9 93326 feed screw, whether it is of the mounting flange type as shown in Fig. 5 or of the "straight spindle" type, which depends on the structural parameters.

Figure 2 shows a fixed plate in which all forming feed screws or conventional feed screws have been removed and the auxiliary feed screws installed in their place. Thus, the formation of cavities is prevented and the concrete mixture is fed solid over the entire cavity formation area and at the same time a driving force is provided for conveying the device along the rails so that the solid "hollow" slab is extruded behind it.

It should be noted that the main purpose of the auxiliary feed screw is to provide a continuous and even supply of the required amount of concrete or concrete-type material throughout the casting or forming chamber in equipment used for the production of concrete products. This mechanism avoids the problem typical of such devices by placing them in the right place in the device, ensuring a smooth, continuous, homogeneous and sufficient flow of material into the forming chamber, resulting in improved casting or forming performance and finished, structurally improved product and each cross section corresponds to and is uniform with all other manufactured cross-sections.

It avoids the problem of material shortages in the forming chambers of such devices, some parts of which have less material than others, although the extrusion process may continue.

The auxiliary feed screw 29 can be used alone or in combination with other auxiliary feed screws or in combination with conventional feed screws 20 such as a "strip feed screw" depending on the desired cross-section of the finished concrete product as shown in Figures 1, 2, 3 and 9.

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The auxiliary feed screw 29 is assembled as follows: A) The central mandrel 35 is a unitary body having the outer surfaces of the upstream end or first portion 33 parallel to each other and the surfaces of the downstream end or second portion 36 tapering to almost zero (as shown in Figure 10); B) Threaded flanges are attached to this shaped center spindle which rotate along its entire length so that: 1. in the first part 33 they have the same diameter and in the second part 36, i.e. at the downstream end, the diameter of the threaded flange decreases uniformly to zero.

2. the pitch of these threaded flanges is uniform along the entire length of the auxiliary feed screw, although the diameter of these threaded flanges decreases toward the downstream end.

3. the angle of the threaded flanges becomes about 12 ° to 15 °. The degree of this angle varies depending on the concrete mix used and its formability varies from plant to plant and depends on the materials available in different geographical areas. Therefore, by varying the angle of the threaded flanges, the auxiliary feed screw can be made to meet certain types of conditions in individual factories. When used with conventional feed screws, this angle corresponds to the angle of the threaded flange of a conventional feed screw.

C) The outer diameter of these threaded flanges and the total length of the auxiliary feed screw depend on the amount of concrete material or are calculated according to the amount of concrete material required to be placed inside the cross section of the forming chamber.

D) Both the spindle and the diameter of the threaded flanges start to taper from the same point towards the downstream end of the auxiliary feed screw, i.e. from the beginning of the second part 36 of the whole auxiliary feed screw (as shown in Fig. 10).

E) The point at the downstream end where the hollow mandrel 35 and threaded flanges 38 begin to taper is dependent on and proportional to: 1. the width of the opening of the feed cone 19 immediately above the auxiliary feed screw mechanism and from which the concrete material flows vertically. This allows the threaded flanges of the auxiliary feed screw to receive sufficient concrete material and transfer this material horizontally into the forming chamber; and 2. The size of the equipment and the finished concrete product available. 6 ", 8", 10 "and 12" extruders require an auxiliary feed screw equal to the depth of the device, for example a 6 "device requires a 4" auxiliary feed screw and an 8 "device requires a 6" auxiliary feed screw to adequately fill the mold or forming chamber. ; and 3. the location or length of the forcing plate 26 immediately at the downstream end of the feed cone 19. The upstream portion of this forcing or vibrating plate is located immediately above the downstream end of the auxiliary feed screw (as shown in Figure 4).

F) The auxiliary feed screw may have either a mounting flange 32 or a straight mandrel for connecting it to the drive mechanism that rotates the auxiliary feed screw. Both methods depend on the product being manufactured with the device.

G) The auxiliary feed screw 29 must be manufactured in two types, one with right-hand threaded flanges and the other with left-hand threaded flanges in order to obtain the correct material distribution and rotation corresponding to conventional feed screws.

The auxiliary feed screw 29 is mounted on the manufacturing device and rotated by its drive mechanism. Due to its structure or shape, the exact or sufficient amount of concrete material is fed to the rotating threaded flanges 34 and 38 and conveyed towards the downstream end 37 of the auxiliary feed screw and the forming chamber between the floor 17, the constraint and leveling plates 26 and 27 and conventional surrounding side plates (not shown). .

As a result of the rotation, the material moves horizontally towards the forming chamber, and due to the rotation, the material also moves into the forming chamber in a radially outward direction, thus filling the cavity of the forming chamber (as shown in Figures 10 and 12).

The taper of both the hollow mandrel 35 and the threaded flanges 38 in the part 36 allows the material to be forced into the forming chamber and filled throughout its cross-section and at the same time, thanks to the tapered structure, prevents the formation material from being destroyed in its cross-section. Not only does the tapered portion feed the concrete material evenly toward the downstream end 37 of the auxiliary feed screw, but as it rotates, the screw automatically discharges the precast concrete material.

In the event that insufficient concrete material is placed at the top of the forming chamber, the method of operation of the auxiliary feed screw ensures that the openings are filled before the final concrete product is compacted and reinforced.

Once the proper tightness of the concrete material has been achieved evenly throughout the cross-section, rotation of the auxiliary feed screw pushes the manufacturing device away from the finished product and ensures a continuous manufacturing process or extrusion of the desired concrete product.

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The auxiliary feed screw can be used in a variety of applications or devices depending on the desired end products.

1. Solid Concrete product e.g. solid floor, ceiling and wall tiles.

A number of auxiliary feed screws replace the conventional feed screws in the extruders 20 of the hollow concrete slabs, and the product thus obtained is a solid floor slab (as shown in Figure 2) and all the auxiliary feed screws are parallel.

It should be noted that the same device used to make hollow floor tiles can be converted to make solid floor tiles simply by replacing conventional feed screws with auxiliary feed screws.

2. An automatic method for filling one or more cavities in a conventional hollow core slab.

Some cavity structures are required to fill one or more cavities to meet certain load criteria. A conventional method of accomplishing this is to make a number of openings in the top surface of the slab, when freshly cast, above a certain cavity, and to fill the openings with a concrete mixture.

This filled cavity then dries and shrinks (usually more than the surrounding slab because it is not compressed) and does not adhere to the surrounding slab material to form a solid body.

By using an auxiliary feed screw at this particular cavity location, the opening in the cavity fills and the filled opening solidifies and becomes integral with the rest of the extruded slab.

The use of the auxiliary feed screw method to fill the cavities 93326 14 ensures that the cross-section is completely homogeneous, as a result of which the structural integrity of the slab is maintained.

When using a combination of a conventional feed screw and an auxiliary feed screw, it should be noted that: a) the longitudinal axes of the feed screws must be parallel; (b) the outer diameter of the auxiliary feed screw is calculated so that the auxiliary feed screw has the same capacity as the conventional feed screw next to it.

3. A large floor slab with four conventional feed screws below and four auxiliary feed screws above to make a slab with four rectangular, vertical cavities.

As already discussed above, in recent years, hollow technology has introduced new slabs with thicker dimensions (larger cross-sectional area) to provide slabs that extend over longer distances and have a higher load capacity for use in parking garages, large terminals and larger buildings. Building regulations require the slab to be lightweight, but still suitable for these longer distances and higher loads.

Currently, there are some extruders that can make 40 cm (16 inch) tiles with four cavities using four conventional feed screws. In this case, the difficulty is that the large area above the conventional feed screws has to be filled with the concrete mixture and pushed over the "hump" of the casting core. Since only a limited amount of mixture can be fed with a conventional feed screw, the concrete tends to push back over the feed screw rather than over the casting core. This causes a defect at the top of the slab, resulting in poor tightness and lower load capacities.

This problem can be solved by placing the auxiliary feed screw above the conventional feed screw. The auxiliary feed screw fills the cavity at the top of the slab, thus providing an even seal and a stronger slab.

4. Manufacture of a hollow core slab with horizontal rectangular cavities.

As shown in Figure 9 and the mechanisms of Figures 7 and 8, it is possible to use this same mechanism to make cavity slabs with horizontal, rectangular cavities. The difference with point 3 above is that the ratio of the auxiliary feed screw to the conventional feed screw is adjacent instead of overlapping.

Claims (7)

1β 93326 1 Ό An apparatus for forming hollow concrete slabs (16; 16A), the apparatus comprising a feed cone (19) for supplying concrete or the like by gravity to a feed screw chamber below, a mold chamber downstream of the feed screw chamber comprising sealing and leveling means (26, 27) for compacting and leveling concrete , a plurality of rotating feed screws (20; 29) horizontally and parallel to each other below the feed cone (19), the feed screws comprising main feed screws (20) each having a stationary shaping mandrel (21) and a finishing tube (23) and a power source (20A) for rotating the feed screws at least one of the feed screws is an auxiliary feed screw (29) having a first upstream portion (33) having a substantially constant diameter and a second downstream portion (36) having a gradually decreasing diameter at the adjacent end of the upstream portion, characterized in that the crimping and leveling means comprise a conveying plate (26) (known per se), the auxiliary feed screw (29) being a core mandrel (35) having a substantially constant diameter at the upstream portion (33) and a gradually decreasing diameter at the downstream portion (36) adjacent thereto; the threaded flange (34) of the auxiliary feed screw (29) has a substantially constant diameter in the upstream portion (33) of the auxiliary feed screw and a decreasing diameter in the downstream portion (36) adjacent the upstream portion (33) to the outermost end (37) of the core mandrel; and the second, downstream, conical portion (36) of the auxiliary feed screw (29) extends into the mold chamber below the compression plate (26) to act against the concrete compacted by the compression plate in the mold chamber. Device according to claim 1, comprising at least one main feed screw extending below the feed cone and having a stationary shaping mandrel at the outermost end of the main feed screw in the mold chamber, characterized in that the auxiliary feed screw (29) is located immediately above the main feed screw (20) parallel thereto . Device according to claim 1, comprising at least one main feed screw extending below the feed cone and having a stationary shaping mandrel at the outermost end of the main feed screw in the sheet metal chamber, characterized in that the auxiliary feed screw (29) is located horizontally and parallel to the main feed screw (20). A device according to claim 1, comprising a plurality of adjacent, parallel main feed screws (20) extending below the feed cone and into the mold chamber and a stationary forming mandrel (21, 23) at the outermost end of each main feed screw in the sheet metal chamber, characterized in that the auxiliary feed screw (29) is located between two adjacent main feed screws. The apparatus of claim 2, wherein each forming mandrel (21, 23) includes a pair of vertical, parallel sides, an arcuately curved convex base, and an upper surface (24, 25), the upper surface including an upstream portion (24) extending from the main feed screw ( 20) upstream of the downstream end (22) forming a guide surface for controlling the direction and flow of concrete passing therethrough, and at the downstream end a horizontal top surface (25) extending downstream of the upward guide surface (24), characterized in that the auxiliary feed screw (29) is located upstream of the lead surface (24) and terminates adjacent the junction (22) between the main feed screw and the shaping mandrel, and the upper surface of the auxiliary feed screw (29) is substantially flush with the horizontal upper surface (25) of the shaping mandrel. 18 93326 Device according to one of the preceding claims, characterized in that the pitch of the auxiliary feed screw (29) is constant from end to end of the feed screw. Device according to claim 6, characterized in that the angle of the threaded flanges of the auxiliary feed screw (29) is about 12 ° to 15 ° from the vertical axis of said screw. Il. 19 93326 Patentkray