WO2010004294A2

WO2010004294A2 - Screed rail apparatus

Info

Publication number: WO2010004294A2
Application number: PCT/GB2009/001719
Authority: WO
Inventors: Rodney Malcolm Arnold; Shaun Anthony Spurrell
Original assignee: Permaban Limited
Priority date: 2008-07-10
Filing date: 2009-07-10
Publication date: 2010-01-14
Also published as: GB0812672D0; GB0814820D0; WO2010004294A3

Abstract

Leave-in-place screed rail apparatus for defining the edges of concrete floor slabs and including two or more substantially vertically-disposed elongate members joined together with yieldable connections, in which the yieldable connections comprise a blind rivet including a cylindrical shell in which is carried a rivet stem, in combination with a flanged collar against which the rivet is set, either the shell of the rivet and/or the flanged collar yielding under tensile forces generated as the concrete of the slabs cures in use to allow the elongate members to separate smoothly and non- incrementally.

Description

Screed Rail Apparatus

This invention relates to screed rail apparatus for use in the formation of concrete floor slabs, especially in the formation of heavy-duty concrete slabs for buildings such as warehouses and retail stores the floors of which are required in use to withstand heavy static loadings and also dynamic forces applied by trolleys, fork-lift trucks and the like as they move across the joints between adjacent slabs.

It is already known, for example from European Patent Application No.03255115.2, to provide leave-in-place screed rail apparatus which includes a divider plate having horizontally-disposed dowels for load transfer between adjacent slabs. The divider plate carries upper edge rails the purpose of which is to protect the upper edges or arrises of the slabs from spalling under loads applied in use. A first edge rail is welded to the divider plate and a second edge rail is connected to the first by yieldable fixings. Each edge rail includes lock means which become embedded in the concrete of its respective slab, thus permanently bonding the edge rails to the slabs so that, as the concrete slabs gradually shrink as the concrete cures, the yieldable fixings permit the edge rails to separate and move apart, whereby they maintain protection or armouring to the arrises of the slabs. Other known screed rail apparatus, such as described on WO 2007/071995, comprises first and second plates secured together in a face-to-face arrangement by yieldable fixings.

Conventionally, in screed rail apparatus of the type described, the yieldable fixings are disposed through apertures formed in the divider plates or edge rails and comprise nylon bolts on which are engaged steel nuts, so that the nylon bolt threads strip under the influence of the nuts as the divider plates or edge rails and are subject to separation forces. However, this results in the separation being incremental, the thread initially resisting being stripped until a certain threshold force is reached, when yielding takes place relatively quickly. This results in uneven stresses being applied to the edges of the concrete slabs through the lock means as curing takes place. In any event, the bolts occasionally and unpredictably suffer total failure at any loading up to approximately 2500N, due either to manufacturing defects or absorption and release of water by the nylon affecting their yield strength and ultimate tensile strength. It is an object of the present invention to provide yieldable edge rail fixing means which avoid the disadvantages of the conventionally-used apparatus, and which preferably allows the fixing means to yield at a predictable separation force.

In one aspect, the present invention provides leave-in-place screed rail apparatus for defining the edges of concrete floor slabs and including two or more substantially vertically-disposed elongate members joined together with yieldable connections, in which the yieldable connections comprise a blind rivet including a cylindrical shell in which is carried a rivet stem, in combination with a flanged collar against which the rivet is set, either the shell of the rivet and/or the flanged collar yielding under tensile forces generated as the concrete of the slabs cures in use to allow the elongate members to separate.

Conventional blind rivets are rivets which are intended to be applied to apertured workpiece members from one side, setting forces being applied from the same side to join the members together. Such blind rivets comprise a cylindrical shell having a radially-enlarged head at one end and a tail end face at the other end. A stem or mandrel is carried in the bore of the shell, the stem having a shank and a domed head the diameter of which is not greater than that of the shell, adjacent the tail end face of the shell. In use, the rivet is inserted, stem head end first, through the apertures, until the shell head contacts the near member. A tensile force is then applied to the protruding end of the stem shank by use of a setting tool, whereby the stem head is urged against the tail end face of the shell and deforms the remote end of the shell against the far member, forming a cup containing the stem head and thus clamping the members together between the pre-formed head of the shell and the deformed remote end. The protruding end of the stem shank may break off, leaving the remaining head end in place within the shell, such rivets being termed "self- plugging" blind rivets.

A flanged collar for use in the present invention preferably comprises a cylindrical part having a radial outer flange at one end. The cylindrical part may be of relatively small or limited axial extent, merely to maintain the collar, and hence the rivet shell, in the correct position with respect to the apertures in the members, or may be longer in axial extent for use with thicker members or to extend further into the apertures formed in the members. For use with apparatus according to the present invention, the flanged collar is disposed in the aperture of the far member, remote from the shell head, so that the remote end of the shell and the domed stem head extend beyond the flanged collar and, on setting the rivet, the remote end of the shell deforms against the flanged collar. The members are thus secured together by the set blind rivet. However, as the concrete of the slabs cures and the edge rails are subject to separation forces, the deformed part of the shell forming the cup may undergo further deformation by cold drawing and passes into the bore of the cylindrical part of the flanged collar, thereby allowing the edge rails to separate smoothly and avoiding the disadvantageous incremental yielding of nylon bolts engaged with steel nuts. Alternatively, depending on the relative strengths and hardness of the material of the shell and flanged collar, the tensile forces exerted by the cup against the flanged collar may cause the collar to fracture, thus allowing the cylindrical part of the collar to move axially together with the shell of the rivet and allowing the elongate members to separate. In some situations, yielding of the connections may take place by a combination of cold drawing and collar fracture.

Preferably, the flanged collar is provided at its flanged end with a countersunk depression, to act as a lead in deformation of the shell cup as it is drawn into the bore of the collar and to provide a zone of weakness to allow fracture yielding to occur at a predictable and reproducible tensile loading.

The elongate members which, in use, are substantially vertically-disposed may in one embodiment comprise edge rails one of which is welded to a divider plate, for example as described in EPA 03255115.2. In another embodiment, the elongate members may comprise face-to-face first and second divider plates, for example as described in

WO2007/071995. Optionally, an intermediate member may be included between the elongate members in either embodiment, especially a member which is resiliently compressed while the yieldable connections remain in place but expands when the yieldable connections allow the elongate members to move apart. In apparatus according to the invention, the elongate members are generally provided with horizontally-disposed slotted apertures through which the yieldable connections are passed. The slots may have variations in width or wall angle due to different material hardnesses, tooling, draft angle on being formed by punching and the like. To accommodate such variations, especially where the members comprise edge rails which are relatively wide, a spring-grip sleeve may firstly be fitted through the slots of the edge rails, while the slots are at least partially in registration, and the rivet shell passed through the bore of the spring- grip sleeve from one end with the location washer being introduced at the other end, before the rivet is set. Spring-grip sleeves, sometimes referred to as slotted spring pins, typically comprise a cylinder formed with a longitudinal through-slot to allow the cylinder to be radially resiliently compressed, an annular chamfer being provided at each end of the cylinder to act as a lead when the sleeve is inserted, generally by tapping with a hammer, in the slots of the edge rails.

Apparatus according to the invention preferably includes studs or other concrete-gripping formations attached to the elongate members and may also include load-transfer dowels attached to or engaged with the divider plate, optionally with sleeves which are applied over the dowels on one side of the divider plate to allow movement between the dowels and sleeves in mutually-orthogonal horizontal directions but to resist relative movement in the vertical direction. The dowels are preferably in the form of flat plates or discs but may optionally be formed with corrugations or other strength enhancing means. In use, the apparatus includes means for adjusting the height above the ground sub-base, to ensure that the concrete slabs, when formed, have essentially horizontal upper surfaces in the same plane from slab to slab.

In another aspect, the invention provides a method of forming concrete floor slabs, the method comprising the steps of erecting leave-in-place screed rail apparatus as hereinbefore described on a ground base to define the adjacent edges of at least two floor slabs, casting concrete on each side of the apparatus and allowing the concrete to cure, whereby the concrete shrinks and the elongate members of the apparatus are subject to separation forces, either the shell of the rivet and/or the flanged collar yielding under tensile forces generated as the concrete of the slabs cures to allow the elongate members to separate. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings of which:

Figure 1 is a general arrangement view of one embodiment of apparatus according to the invention incorporating a divider plate and edge rails;

Figure 2 is a general view of another embodiment of apparatus according to the invention, incorporating first and second divider plates;

Figure 3 is a fragmentary plan view of the apparatus as shown in Figure 1, viewed as a horizontal section along the line III-III, showing the rivet components in position before setting the rivet;

Figure 4 is similar to Figure 3 but shows the rivet having been set; and

Figure 5 is similar to Figure 4 but shows the edge rails separated in one yielding manner; and

Figure 6 is similar to Figure 4 but shows the edge rails separated in another yielding manner.

Referring firstly to Figure 1, the apparatus consists essentially of a vertically-disposed divider plate member 11 formed at its upper end with a horizontal ledge 12 and, optionally, an upstanding lip 12A, a first edge rail 13 being welded to the ledge 12. A second edge rail 14 is attached to the rail 13 by yieldable fixings 15, as hereinafter described in more detail. The divider plate carries horizontal dowel plates 16 which extend on both sides of the divider plate; sleeves 17 are optional but, if required, are placed over the dowel plates on one side of the divider plate to allow relative movement in mutually orthogonal horizontal directions as the concrete of the subsequently-cast slabs cures, while resisting relative vertical movement. Each edge rail 13, 14 carries studs 18, 19 which, in use, become embedded in the concrete of the respective slabs on either side of the apparatus so that, as the concrete shrinks on curing, the edge rails remain firmly bonded to the respective slabs as the fixings 15 yield. Referring now to Figure 2, the apparatus consists essentially of a first divider plate 21 to which is attached a second divider plate 22, shallower than plate 21, by yieldable fixings 23. The divider plates are disposed in face-to-face configuration and their upper edges are respectively turned over outwardly and downwardly, to form a horizontal part with an outer depending lip to each plate, the horizontal parts being co-planar and intended, in use, to define the upper surface of the cast concrete. In a manner similar to that described with reference to Figure 1, the divider plate 21 carries horizontal dowel plates and optional sleeves 24.

Referring now to Figure 3, the edge rails 13, 14 are provided with spaced-apart apertures which may be in the form of circular holes or elongate slots 31, 32. With the slots at least partly in registration, a spring-grip sleeve 33 is tapped into position temporarily to hold the edge rails together. A cylindrical collar 35 having a countersunk flange 34 is then applied from one side, with the collar 35 located within the spring-grip sleeve 33. The shell 36 of a blind rivet is inserted through the bore of the 35 from the other side, via a plane washer 37 between the outer face of the rail 14 and the flange of the radially-enlarged head 38 of the rivet shell. The rivet has a stem 39 carried within the bore of the shell, the stem having a domed head 40 adjacent the tail end face of the shell.

Referring now to Figure 4, the rivet has been set by applying a riveting tool to the radially- enlarged head 38 of the shell and applying a tensile force to the stem 39. As a result, the head 40 of the stem has been drawn into the tail end region of the shell, deforming the metal thereof radially outwardly to form a cup 41 within the countersink of the flange 34 of the collar, the cup serving to locate the head 40 of the rivet stem. The protruding portion of the rivet stem has been broken away essentially flush with the head of the shell. The members 13, 14 are thus secured together by the set rivet acting between washer 37 and the flange 34 of the location washer.

Referring now to Figure 5, the concrete is cured and has shrunk and, as a result, the edge rails 13, 14 have been subject to separation forces. Under the separation forces, the cup 41 of the rivet shell and has been cold-drawn with plastic deformation into the bore of the collar 35, to form a plain cylindrical region 41a, thereby allowing the rails to separate smoothly.

Referring to Figure 6, the concrete has cured and, in an alternative manner of yielding to that shown in Figure 5, the collar part 35 of the flanged collar has separated from the flange 34 by fracture 42, whereby the collar together with the cup 41 end of the rivet shell have moved axially within the bore of the sleeve 22 to allow the rails to separate.

It has been found that deformation of the cup 41 to form the cylindrical region 41a takes place, with aluminium rivets and aluminium collars, at lower forces than where the collars are die cast from, for example, a zinc alloy. With aluminium collars, yielding takes place by cold drawing whereas, with die cast collars, yielding takes place by fracture of the collar at the flange. According to either mode of yielding, the yield point is consistent and predictable by choice of materials and collar design, in particular the thickness of the collar at the transitional zone to the flange.

Claims

1. Leave-in-place screed rail apparatus for defining the edges of concrete floor slabs and including two or more substantially vertically-disposed elongate members joined together with yieldable connections, in which the yieldable connections comprise a blind rivet including a cylindrical shell in which is carried a rivet stem, in combination with a flanged collar against which the rivet is set, either the shell of the rivet and/or the flanged collar yielding under tensile forces generated as the concrete of the slabs cures in use to allow the elongate members to separate.

2. Apparatus according to claim 1, in which the flanged collar comprises a cylindrical part having a radial outer flange at one end.

3. Apparatus according to claim 2, in which the flanged collar is provided at its flanged end with a countersunk depression.

4. Apparatus according to any preceding claim, in which the elongate members comprise upper edge rails to define the upper surface level of the concrete slabs, one edge rail being welded to a divider plate.

5. Apparatus according to any of claims 1 to 3, in which the elongate members comprise face-to-face first and second divider plates the upper edges of which define the upper surface level of the concrete slabs.

6. Apparatus according to any preceding claim and including studs or other concrete-gripping formations attached to the elongate members.

7. Apparatus according to any preceding claim and including load-transfer dowels optionally with sleeves which are applied over the dowels to allow movement between the dowels and sleeves in mutually-orthogonal horizontal directions but to resist relative movement in the vertical direction as the concrete cures in use.

8. A method of forming concrete floor slabs, the method comprising the steps of erecting leave-in-place screed rail apparatus according to any of claims 1 to 7 on a ground base to defined the adjacent edges of at least two floor slabs, casting concrete on each side of the apparatus and allowing the concrete to cure, whereby the concrete shrinks and the elongate members of the apparatus are subject to separation forces, either the shell of the rivet and/or the flanged collar yielding under tensile forces generated as the concrete of the slabs cures to allow the elongate members to separate.

9. A method according to claim 8, in which part of the rivet shell is deformed on setting the rivet to form a cup, the cup undergoing further deformation under tensile separation forces to pass into the bore of the flanged collar.

10. A method according to claim 8, in which part of the rivet shell is deformed on getting the rivet to form a cup, the tensile separation forces exerted by the cup on the flanged collar causing the collar to yield by fracture.