WO2005111332A2

WO2005111332A2 - A load plate and method of casting adjacent slabs of concrete

Info

Publication number: WO2005111332A2
Application number: PCT/IB2005/001266
Authority: WO
Inventors: David Peter Samson
Original assignee: David Peter Samson
Priority date: 2004-05-14
Filing date: 2005-05-13
Publication date: 2005-11-24
Also published as: WO2005111332A3; ZA200610610B

Abstract

The invention provides a load plate (1; 21) for connecting concrete slabs and a method of casting adjacent concrete slabs. The load plate has a central region (3) connected by converging sides (4) to a first end (2.1). An anchoring formation (7; 23), which is preferably at least one hole through the plate, is provided between the central region (3) and the second end (2.2). The load plate has an octagonal shape with a strip of compressible material (6) secured to each of its sides (5) at the central region (3) respectively. The plate will optionally include a slot (23) for a locating screw (24) adjacent the anchoring formation or such a slot may form the anchoring formation (23). The method of the invention includes allowing the first slab of concrete to set over the load plate through a shutter, removing the load plate and shutter, putting the load plate back into the first slab, and pouring a second slab. The plate's anchoring formation (7; 23) secures it in the second slab.

Description

A LOAD PLATE AND METHOD OF CASTING ADJACENT SLABS OF CONCRETE

FIELD OF THE INVENTION

The invention relates to a load plate for connecting adjacent slabs of concrete and extends to a method of casting adjacent slabs of concrete.

BACKGROUND OF THE INVENTION

The use of dowels to connect adjacent slabs of concrete cast on the ground is well known. These dowels may be of circular or square cross-section. The dowels are provided to extend between and into the adjacent slabs. Different methods are used to get the dowels in place in a first concrete slab. These methods include the use of sacrificial sleeves which are cast into the first slab. A shutter or side form, as it is also known, defines the edge of the first concrete slab and is generally provided as a flat length of metal or wood. After removal of the shutter, with the dowels in place extending from the edge of the first slab, a second slab can be poured.

The dowels provide for stress distribution under load across the join line between the slabs. The connection provided is against vertical shifting between the slabs. The shrinking of setting concrete must preferably not be restrained at the edge of a slab by the shape of the dowel over which the slab has been poured. Misalignment of the dowels relative to each other may prevent the join from relieving stresses which develop when the concrete shrinks. This can cause random cracks to form in the concrete.

The specification of US 6,354,760 discloses a square load plate directed at some of the problems with prior art dowels. The load plate is located in a first slab using a plastic triangular sheath. This is done by placing the sheath over a transverse extension from a shutter against which the first slab is poured. When the concrete has set the shutter is removed leaving the sheath in the slab. The sheath is sized to receive half of the plate with the other triangular half extending outwardly from the edge of the first slab. A second adjacent slab can then be poured against the first one, over the free half of the load plate. This load plate is limited to be used with the specific shutters and sacrificial sheathes. This ancillary equipment comes at cost, which can be prohibitive for some building projects.

OBJECT OF THE INVENTION

It is an object of this invention to provide a novel load plate for connecting adjacent slabs of concrete and a method of casting such slabs, both of which are to at least partially alleviate the above problems and limitations.

SUMMARY OF THE INVENTION

In accordance with a first aspect of this invention there is provided a load plate for connecting concrete slabs having a central region located between two opposite ends and an anchoring formation provided between the central region and one end.

The invention further provides for the central region to be connected by converging sides to the other end; and for the anchoring formation to be at least one hole through the plate. The central region is preferably connected by converging sides to both ends. Further features of the invention further provide for the sides at the central region to be substantially parallel to a longitudinal axis through the ends; for the sides at the central region to be flat; and for a strip of compressible material to be secured to the sides at or adjacent the central region.

Further features of the invention provide for there to be at least one slot for a locating screw to the side of the central region with the anchoring formation; and for the slot to be part of a hole providing the anchoring formation.

Further features of the invention provide for ends to be flat and perpendicular to the longitudinal axis; for the plate to be symmetrical; and for the plate to have an octagonal shape.

In accordance with another aspect of this invention there is provided a method of casting adjacent concrete slabs comprising pouring a first slab of concrete against a shutter and over half of a load plate extending therethrough, allowing the first slab to set, removing the load plate from the shutter and the slot formed around it in the concrete, removing the shutter from the edge of the first slab, inserting the load plate back into the slot in the concrete, and pouring a second slab of concrete against the first slab and over the other half of the load plate extending therefrom.

The invention further provides for the load plate to be releasably secured through the shutter before the first slab is poured; and for a locator shaped to receive half of the load plate to be used to position the load plate through the shutter.

Further features of the invention provide for the half of the load plate to extend through the shutter to be treated with a bond-breaker before the first slab is poured; and for the load plate to be as defined above and the second slab poured over the half with the anchoring formation.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will become apparent from the following description, by way of example only, with reference to the accompanying drawings in which

Figure 1 is plan view of one embodiment of a load plate;

Figure 2 is a part cross-sectional side view of the load plate in Figure 1 secured through a shutter; Figure 3 is a part cross-sectional plan view of another embodiment of a load plate also secured through a shutter; Figure 4 is a plan view of a first load plate locator; and

Figure 5 is a cross sectional side view of a second locator against a shutter.

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figures 1 and 2, a load plate (1) for connecting concrete slabs is shown. The load plate (1 ) has an octagonal shape with first (2.1) and second (2.2) opposite ends. The ends (2) are connected to a central region (3) of increased width by inclined sides (4). The sides (4) converge from the central region (3) towards the ends (2).

The sides (5) at the central region (3) are flat and parallel to a longitudinal axis (L) through the ends (2). A strip of compressible material (6) is secured to the flat sides (5) at the central region (3) respectively.

In accordance with this invention, an anchoring formation (7) is provided between the central region (3) and the second end (2.2). The formation will preferably be at least one hole (7) through the plate (1). PC

The form of the plate (1) provides a release angle between the central region (3) and ends (2), and more significantly between the central region (3) and the first end (2.1).

In Figure 2, the load plate (1) is shown secured in position through a longitudinal locating slot (13) in a metal shutter (10) for casting concrete slabs. The load plate (1 ) is held in a releasably securable manner against a support (11). The support in this embodiment is a sleeve (11 ) secured over the locating slot (13) in the shutter (10) and fixed thereto by screws (12). The sleeve (11) is provided with a fastening screw (14) through a correspondingly threaded aperture in its wall.

In use, a first concrete slab is poured against the shutter (10) over the load plate (1 ) secured to extend therethrough as already described. Before this is done the half of the load plate (1 ) extending oppositely to the sleeve (11 ) is treated with a bond- breaker. This is the half which is without the anchor (7) and over which the first slab is poured. The bond-breaker is required to deter bonding of the setting concrete to the plate (1 ). This in turn enables removal of the plate (1 ) as described below.

The term "bond-breaker" is to be given a broad meaning in this specification. Various suitable compounds which serve this purpose will be within the competence of a person skilled in the art.

Once the concrete of the first slab has set to a sufficient degree, the fastening screw (14) is loosened, releasing the load plate (1). A bar or other suitable instrument is then placed in the hole (7) and used to lever the load plate (1 ) from the concrete slab and out of the sleeve (11 ). The significance of the release angle between the central region (3) and the first end (2.1) will be appreciated here. An impact hammer, which is usually available on construction sites, can also be conveniently used to remove the plate (1 ). A shutter (10) will have a plurality of load plates (1) spaced apart along its length and each of these is removed.

Next, the shutter (10) is removed from the edge of the first slab. This done by cleaving the shutter (10) from the concrete edge, starting at one end of the shutter (10) and progressively inserting wedges between the shutter (10) and the edge as they are parted. It is desirable that the shutter (10) be parted in a direction generally perpendicular to the concrete edge rather than shearing the shutter (10) upwardly from the edge. This is because the latter tends to cause pieces of the concrete to break out from the edge.

The load plate (1 ) is then inserted back into the slot which it formed in the set concrete. A second slab of concrete is poured against the first slab and over the half of the load plate (1) extending therefrom with the anchoring formation (7). The second slab sets with a plug of concrete formed through the hole (7).

The sleeve (11) and screw (14) provide for secure alignment of the load plate (1) while handling the shutter (10) and during pouring and setting of the concrete.

Whereas the square shaped prior art load plate requires careful alignment of two opposite comers on the join line between two slabs, the load plate (1) of the present invention has flat sides (5) in the central region (3) and these are lined with the compressible material (6). This construction provides a degree of tolerance in the required alignment. The compressible material (6) enables movement of the concrete at the edges of the slabs without obstruction by the load plate (1). The shape of the load plate ( ) also provides more efficient distribution of imposed stresses avoiding point loads.

It will however be appreciated that the half of the plate (1 ) with the anchor formation (7) need not be shaped with a release angle. The purpose of this side is to be fixed in the second slab. However, the symmetry in the shape of the load plate (1 ) shown contributes to the efficient and even load distribution across the join.

The compressible material (6) can be of any suitable type. It is selected to give way under shrinkage of the concrete but to hold the fresh concrete away from the load plate (1 ) when it is poured. An adhesive tape made of compressible material is one convenient example. It will be appreciated that this use of compressible material will find application at different positions on the outer surface of load plates of various constructions.

Referring now to Figure 3, another embodiment of a load plate (21) is shown. While the shape is the same as that in Figures 1 and 2, the plate (21) has an anchor formation in the form of a longitudinal slot (23) for a locating bolt or screw (24).

The load plate (21) is positioned through a locating slot (26) in a shutter (27), which is in this embodiment a length of wooden plank. A support (28), conveniently provided from a length of angle iron, extends perpendicularly to the shutter board (27) to one side from adjacent the slot (26). This arrangement can also be seen in Figure 5.

While the thickness of shutter boards (27) used may vary, it is important that half the load plate (21 ) extends from the side of the shutter board (27) opposite to the support (28). This freely extending half is the one over which a first concrete slab will be cast.

The support (28) has a threaded screw hole (not shown) corresponding to the screw (24). Once the load plate (21) is in the slot (26), its position can be adjusted to that required. The screw (24) is then tightened, releasably securing the load plate (21) against the support (28). The screw (23) will conveniently be adapted for use with an Allen key. With the adjustability of position afforded by the slot (23), the load plate (21) together with the system of fastening it to the support (28) can be used with shutters (27) of various widths. This includes shutter boards made from metal in addition to those made of wood.

A load plate may also be provided with a pair of parallel slots (not shown), each with its own locating screw. This arrangement will deter against lateral tilting of the load plate. The anchor formation may also be provided with the form of a key-hole slot, from a combination of a slot with an enlarged opening adjacent the end of the plate. The enlargement will easily receive an impact hammer or bar used to remove the load plate from the first cast slab. Figures 4 and 5 respectively show two embodiments of a locator (31) for use in correctly positioning a load plate (21) through a shutter board (27). The locators (31) are configured to receive half of a load plate (21). Each locator (31) has a body (32) which, in use, engages against a shutter (27) along one flat side (33) thereof. A recess (34) suitably shaped to correspond to half a load plate (21) extends into the body (32) from the side (33).

The locator (31) in Figure 4 is simply a length of wooden plank with the recess (34) cut into it. The one in Figure 5 is moulded from plastics material, with the recess provided as a socket (34). The locator (31) is removably beatable over a load plate (21) extending through a shutter board (27), like those shown in Figures 2 and 3. The locator (31) is held perpendicular with its side (33) against a shutter board (27). It will be appreciated that the locator could also, for example, be a suitably configured metal frame. The locator (31) can either be used to correctly position the load plate (1 ; 21) before screw (14; 24) is tightened, or it can be used to check accuracy of load plate positioning before concrete is poured. In the latter instance, a spirit level may be usefully secured to the locator (31).

In some cases, a wooden shutter may be used having locating slots into which the load plates (21) are respectively an interference fit. No additional means, other than frictional engagement, is provided to hold the load plates (21) in position. The locator (31 ) will assist when manipulating the load plates (21) into position in such a shutter.

The load plate (1) is cut from metal, however, any material of suitable strength may also be used. While the sides (2) of the load plate (1) shown are provided to be straight with the sides (5) at the central region (3) and ends (4) flat, it will be appreciated that the plate can also have curved sides or, more specifically, have a substantially elliptical shape.

While the presence of an anchoring formation as a hole or slot (7; 23) is preferred because it makes the plate (1 ; 21) cheaper to manufacture and is also useful when prying the plate from the first slab, the formation (7; 23) may also be provided by a protrusion on the plate (1 ; 21 ). Such a protrusion may also be in the form of an outward step along the side of the plate (1 ; 21) or provided by a lateral bend across the plate (1 ; 21 ).

The half of the load plate (1 ; 21 ) fixed by the plug of concrete through the hole (7; 23) will be fixed relative to the second slab. However, the half treated with the bond- breaker will move relatively easily in the first slab. This connection will provide for more reliable crack control.

The invention provides that there are no sacrificial components; with all, save the load plate which remains in the concrete, being reusable. Improved load distribution will allow load plates to be spaced further apart and, thus, fixing of adjacent slabs with fewer load plates. It will be appreciated that the same advantages can also be obtained using an elliptical load plate, as mentioned above, with substantially flat sides on the middle portion that operatively extends between adjacent slabs.

It will be appreciated by a suitably skilled person that further variations to the described embodiments may be made without departing from the scope of the current invention.

Claims

1. A load plate for connecting concrete slabs having a central region located between opposite ends and an anchoring formation provided between the central region and one end.

2. A load plate as claimed in claim 1 in which the central region is connected by converging sides to the other end.

3. A load plate as claimed in claim 1 or claim 2 in which the anchoring formation is at least one hole through the plate.

4. A load plate as claimed in claim 2 or claim 3 in which the central region is connected by converging sides to both ends.

5. A load plate as claimed in any one of the preceding claims in which the sides at the central region are substantially parallel to a longitudinal axis through the opposite ends.

6. A load plate as claimed in claim 5 in which the sides at the central region are flat.

7. A load plate as claimed in any of the preceding claims in which a strip of compressible material is secured to the sides at or adjacent the central region.

8. A load plate as claimed in any of the preceding claims which includes at least one slot for a locating screw to the side of the central region with the anchoring formation.

9. A load plate as claimed in claim 8 in which the slot provides the anchoring formation.

10. A load plate as claimed in any of the preceding claims in which the ends are flat.

11. A load plate as claimed in claim 10 which has an octagonal shape.

12. A method of casting adjacent concrete slabs comprising: pouring a first slab of concrete against a shutter and over half of a load plate extending therethrough, allowing the first slab to set, removing the load plate from the shutter and the slot formed around it in the concrete, removing the shutter from the edge of the first slab, inserting the load plate back into the slot in the concrete, and pouring a second slab of concrete against the first slab and over the other half of the load plate extending therefrom.

13. A method as claimed in claim 12 in which the load plate is removably secured through the shutter before the first slab is poured.

14. A method as claimed in claim 13 in which a locator shaped to receive half of the load plate is used to position the load plate through the shutter.

15. A method as claimed in any one of claims 12 to 14 in which the half of the load plate to extend through the shutter is treated with a bond-breaker before the first slab is poured.

16. A method as claimed in any one of claims 12 to 15 in which the load plate is as claimed in any of claims 1 to 11 and the second slab is poured over the half with the anchoring formation.