EP2510248A1

EP2510248A1 - Frangible connector for clamping two plates together

Info

Publication number: EP2510248A1
Application number: EP10805782A
Authority: EP
Inventors: Trent Davis; Tapio Laiho
Original assignee: Peikko Group Oy
Current assignee: Peikko Group Oy
Priority date: 2009-12-08
Filing date: 2010-12-07
Publication date: 2012-10-17
Also published as: GB2476055B; CN102648355A; GB2476055A; WO2011070004A1; CN102648355B; GB0921505D0

Abstract

The invention relates to a frangible connector for clamping two plates together. The connector comprises a distal flange (4); a proximal flange (2); and a shaft (3) between the flanges (2, 4). In use, the connector is inserted into slots (S) in the plates in a first orientation until the distal flange (4) passes fully through the slots (S). The connector is rotatable to a second orientation in which the plates are clamped between the flanges (2, 4). The shaft (3) has deformable portions so that, as the connector is rotated, the deformable portions deform until it reaches the second orientation. Part of the connector is frangible so that, when subjected a load above a threshold value, the connector fails such that the clamping force between the flanges is lost.

Description

FRANGIBLE CONNECTOR FOR CLAMPING TWO PLATES TOGETHER

The present invention relates to a frangible connector for clamping two plates together.

The invention has been specifically designed for the joint system for a concrete floor. However, it is broadly applicable to the situation where two plates elements are required to be temporarily clamped together face to face, but are then required to subsequently move away from one another under a load perpendicular to the plane of the plates .

One such joint system is known as the Peikko TERA joint disclosed in EP-A- 1123443.

Such a joint is used for floors of large buildings such as warehouses and superstores. The floor consists of a number of concrete slabs which are cast in place. The joints define the space into which the concrete is cast. Each joint is provided with a pair of edge rails one for each adjacent slab each having a number of anchors which anchor into the concrete on each side of the joint. As the concrete cures, it shrinks and the rails are pulled apart from one another to provide edge protection for the

concrete. The rails must be held together in alignment during the transportation and pouring process and ensure that they are easy to handle, but must also be able to move apart as the concrete shrinks.

In order to hold the rails together, frangible bolts, for example of nylon, are used to connect the rails. Each bolt is secured by a nut and is surrounded by a split sleeve to provide additional rigidity to the nylon bolt and

maintain the correct alignment during transportation and installation. Such an arrangement is disclosed, for example, in EP 1867783.

Each connector comprises three separate parts. In order to install a single connector, the plates are first held in alignment such that corresponding connection holes are aligned. The sleeve is tapped into place, the bolt is then pushed through the hole and the nut is placed over the threaded end of the bolt. The nut is started using fingers and is then tightened using an electric screwdriver. Such a process is repeated numerous time along the length of a rail.

The present invention provides a connector which is simpler to manufacture and install. According to the present invention there is provided a frangible connector for clamping two plates together, each plate having an aligned slot having an elongate

configuration,

the connector comprising:

a distal end and a proximal end spaced along an axis; an engagement head at the proximal end;

a distal retaining flange towards the distal end;

a proximal retaining flange distally of the engagement head; and

a shaft between the distal and proximal flanges;

the connector being insertable, in use, into the aligned slots in the plates in a first orientation until the distal flange has passed fully through the slots and being rotatable about the axis to a second orientation in which the plates are clamped, in use, between the distal and proximal flanges;

the shaft having a cross section with an elongate shape, the longest dimension of which corresponds, in use, to the shortest dimension of the slot and the shaft having deformable portions, so that, in use, as the connector is rotated to the second orientation, the deformable portions deform until it reaches the second orientation, in which the longest dimension is arranged to fit tightly within the shortest dimension of the slot;

part of the connector being frangible so that, when subjected, in use, to an axial load direction, the connector fails in the sense that the clamping force between the distal and proximal flanges is lost.

The present invention essentially provides a frangible twist-lock connection that can clamp two plates in an axial and a lateral sense. The connector is inserted into the slots in the plate and twisted to the second orientation. This fulfils two functions. Firstly, the distal and

proximal retaining flanges clamp the plates together against separation, and secondly the tight fit of the shaft across the shortest dimension of the slots then prevents

misalignment between the plates.

As the connector is frangible, it allows the plates to move apart when subjected to a separating force as the concrete shrinks. The connectors are designed to be robust enough to withstand transportation and installation of the plates, but will fail readily under the type of load experienced as the concrete shrinks, typically, at a load in order of magnitude less than a load which would otherwise damage the concrete. The connector is a single component and there is no need for a sleeve or nut so that it can be easily

manufactured. Also, the simple twist-lock procedure will improve the speed of assembly of the rails by an order of magnitude .

Although not necessary in the broadest sense, the connector lends itself very well to being a one piece moulding, for example an injection moulding, allowing it to be manufactured cheaply and easily.

Each of the faces of the flanges which face the shaft may be flat. However, this means that the connector has to be made with very precise tolerances in order to ensure that the connector is able to clamp the plates in the second orientation. Therefore, preferably, at least one of the flanges is provided with a feature to generate an axial clamping force as it is rotated to the second orientation. Such a feature means that, in use, the manufacturing

tolerances of the connector and slot are less critical and that sufficient clamping force can be generated in a

connector which can still readily be manually turned to the second orientation.

Preferably the feature takes the form of the proximally facing surface of the distal flange having a cam surface which, upon rotation of the connector from the first orientation, provides a lead-in surface to allow the axial clamping force to be generated on the plates between the flanges. Alternatively or additionally, the feature may be a recess on the distally facing surface of the proximal flange which fulfils the same function.

The deformable portions could, for example, be an insert of a material which has a resilience of less than the resilience of the rest of the connector. However,

preferably, the deformable portions are configured so that, once in the second orientation, they lock the connector against rotation away from the second orientation. By preventing counter rotation of the connector, the deformable portions prevent the connector from accidentally becoming dislodged once in place.

One way to achieve this is for the resilient portions to be a pair of diametrically opposed resilient tabs, each being spaced from a main body of the shaft, each resilient tab being configured to be deformed by the slots towards the main body of the shaft as the connector is rotated into the second orientation, and snapped back into the original orientation as the connector approaches the second

orientation, whereupon engagement of the tabs with the shortest dimension of the slot prevents counter rotation of the connector. Such a connector can readily be twisted to the second orientation but, once there, is locked against counter rotation. The tabs could be integral with the rest of the connector or could be made of a second material such as a metal .

The engagement head may be a handle that is manually gripped or may be a hole, slot or specially shaped (e.g., hexagonal) head for engagement with a tool such as a

screwdriver, socket or alien key. The handle preferably has a flat configuration as this provides a visual indication of the rotational orientation of the connector. Preferably, the proximal end of the handle is devoid of straight edges as, if it had a straight edge, there would be a number of straight edges aligned along the rail potentially generating a weakness in the surrounding concrete. The handle may be provided with one or more through holes allowing the

concrete to "key" into the handle.

Either or both of the shaft and flanges could be designed to be frangible. However, the current preference is for the distal retaining flange to be frangible in preference to the shaft or proximal flange. The distal flange naturally has small shoulders and preferably, the cross section of these shoulders in the plane of the outer extremity of the shaft in the longest dimension is designed so that the shoulders of the proximal flange will shear in preference to any other failure mechanism.

An example of a connector in accordance with the present invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of the connector from the distal end;

Fig. 2 is a perspective view of the connector from the proximal end;

Fig. 3 is a plan view of the connector from the

proximal end; Fig. 4 is a plan view of the connector from the distal end;

Fig. 5 is a perspective view from the distal end which has been cut in a plane perpendicular to the axis of the connector to show the cross section of the shaft;

Fig. 6 is a perspective view from the proximal end which has been cut in a plane parallel to but offset from the axis of the connector showing the structure of the shaft ;

Figs. 7A-7G are schematic cross-sections of the shaft in the slot in showing it in various rotational positions as it is twisted from an insertion position to a locked

position;

Fig. 8 is a perspective view of a second example of a connector;

Fig. 9 is a top view of the second connector;

Fig. 10 is a side of a second connector; and

Fig. 11 is an end view of the second connector. The connector is injection moulded and may be made from a wide variety of materials including metals, composites, and polymers . It is preferably made from a low cost

polymeric material for ease of production and low unit cost. If desired, the injection moulding may be internally re- inforced or strengthened by a structural element such as a metal, or other material, plate. Such a structural element would be moulded into the connector during the injection moulding process as is well know in the art. The connector consists of four sections, namely, beginning from the proximal end, a handle 1, proximal flange 2, shaft 3 and distal flange 4 which will be described in more detail below.

The handle 1 has a flat plate-like configuration which has perpendicular reinforcing webs 5 which extend to the proximal flange 2. The proximal end of the handle has a curved configuration to reduce potential lines of weakness in the surrounding concrete. It may also be provided with through-holes (not shown) to key into the concrete. The handle is large enough that it can easily be gripped by the hand of a user and, as such, it has a length and width of around 2 to 3 cm.

The proximal flange 2 has a flat disk- like

configuration.

The shaft 3 has a cross section with the largest lateral dimension X (see Fig. 7) corresponding to the narrowest dimension of the elongate slot S into which the connector is fitted. The length of the shaft is determined by the thickness of the two plates to be clamped and is typically between 1 and 3 cm. The shaft has a pair of resilient tabs 6 which are resiliently connected to and spaced from a main body 7 of the shaft. As best shown in Figs. 1 and 2, these tabs 6 extend for almost the full axial length of the shaft, but are free at their axial ends to allow them to deflect. The shaft 3 has a pair of end faces 8 which are flat. The tabs 6 have corresponding end faces 9 which are coplanar with respective end faces 8 of the main body 7. Each of the end faces 8 leads to a curved shoulder

10. The distal flange 4 has a tapered portion 11 at its distal end to facilitate insertion into the slot. The proximally facing surface of the distal flange is generally flat, but is provided with a pair of diametrically opposed cam surfaces 12 for the reason set out below.

The use of a connector will now be described with particular reference to Figs. 7A-7G. A number of connectors are inserted along the length of the plane of aligned rails. The aligned rails each have a plurality of elongate slots S, respective pairs of which are aligned. In practice, the slots will be elongated in the direction which, in use, would be horizontal, but the connectors could work equally in any orientation.

The connector is inserted into a pair of aligned slots assisted by the tapered portion 11 on the distal flange 4 until the distal flange 4 passes fully through the slot. All that is then required is a 90° turn about the axis of the connector to complete the connection.

This 90° turn fulfils a number of functions. Firstly, the cam surfaces 12 on the proximal face of the distal flange provides a lead-in surface which, upon rotation, draws the two plates together so that the distal flange and the proximal flange clamp the two plates together.

Secondly, as the connector rotates in the direction of arrow Y (see Fig. 7B) the tabs 6 are caused, by the narrow dimension of the slots S, to deflect towards the main body 7. With the tabs 6 deflected inwardly, the shaft is able to rotate in the slots. Once the ends of the tabs 6 have passed the narrowest dimension of the slot, they are free to spring back under their own resilience. In this

orientation, (shown in Fig. 7G) the end faces 8 of the main body and the end faces 9 of the tabs 6 are aligned and bear against the walls of the slot across the narrow dimension to clamp the plates against relative vertical movement. In this position, the tabs 6 prevent counter rotation of the connector as they are now unable to deflect back towards the body 7 of the shaft when a counter rotational force is applied to the connector.

The distal flange 4 has a pair of failure planes Z one of which is shown in Fig. 1 and both of which are shown in Fig. 4. At each of these locations, the distal flange 4 has a cross section which is . smaller than the cross section of the shaft 3. The axial loading on the connector is applied between the proximal flange 2 and distal flange 3. Under such loading, the distal flange 4 will shear at one or both of the failure planes Z, and the clamping force is lost allowing the plates may move apart in the axial direction. Typically, each connector is designed to have a breaking strength of 10 to 30KN, but may be higher or lower as required.

A second example of a connector is shown in Figs. 8 to

11.

This is the same in most respects as the first example and the same reference numerals have been used to designate the same components. There are two primary differences. Firstly, the handle 1 of the first example has been replaced with a socket. In this case, the socket is hexagonal to receive a hexagonal tool, but could be any appropriate shape corresponding to the chosen tool. Also, secondly, a pair of diametrically opposed

recesses 21 (only one of which is shown in the figures) are provided in the distally facing surface of the proximal flange 2. This complements the cam surfaces 12 in providing the clamping force when the connector is rotated to the locked position. In an alternative construction, the

recesses 21 may be provided instead of the cam surfaces 12.

Claims

CLAIMS : -

1. A frangible connector for clamping two plates together, each plate having an aligned slot (S) having an elongate configuration,

characterized by the connector comprising:

a distal retaining flange (4) towards the distal end; a proximal retaining flange (2) distally of the

engagement head; and

a shaft (3) between the distal and proximal flanges (4,

2) ;

the connector being insertable, in use, into the aligned slots (S) in the plates in a first orientation until the distal flange (4) has passed fully through the slots (S) and being rotatable about the axis to a second orientation in which the plates are clamped, in use, between the distal and proximal flanges (4, 2) ;

the shaft (3) having a cross section with an elongate shape, the longest dimension (X) of which corresponds, in use, to the shortest dimension of the slot (S) and the shaft (3) having deformable portions, so that, in use, as the connector is rotated to the second orientation, the

deformable portions deform until it reaches the second orientation, in which the longest dimension is arranged to fit tightly within the shortest dimension of the slot (S) ; part of the connector being frangible so that, when subjected a load above a threshold value in the axial direction, the connector fails in the sense that the

clamping force between the distal and proximal flanges (4, 2) is lost.

2. A connector according to claim 1, wherein the connector being a one piece moulding.

3. A connector according to claim 1 or claim 2, wherein at least one of the flanges (4, 2) is provided with a feature to generate an axial clamping force as it is rotated to the second orientation. 4. A connector according to claim 3, wherein the feature takes the form of the proximally facing surface of the distal flange (4) having a cam surface (12) which, upon rotation of the connector from the first orientation, provides a lead-in surface to allow the axial clamping force to be generated on the plates between the flanges (2,

4) .

5. A connector according to any one of the preceding claims, wherein the deformable portions are configured so that, once in the second orientation, they lock the

connector against rotation away from the second orientation.

6. A connector according to claim 5, wherein the

deformable portions are a pair of diametrically opposed resilient tabs (6) , each being spaced from a main body (7) of the shaft (3) , each resilient tab (6) being configured to be deformed by the slots towards the main body (7) of the shaft (3) as the connector is rotated into the second orientation, and snapped back into the original position as the connector approaches the second orientation, whereupon engagement of the tabs (6) with the shortest dimension of the slot prevents counter rotation of the connector.

7. A connector according to any one of the preceding claims, wherein the engagement head is a handle (1) with a flat configuration.

8. A connector according to claim 7, wherein the proximal end of the handle (1) is devoid of straight edges.

9. A connector according to any one of the preceding claims, wherein the distal retaining flange (4) is frangible in preference to the shaft (3) or proximal flange.