EP1486629A2

EP1486629A2 - Fixing Devices

Info

Publication number: EP1486629A2
Application number: EP04102483A
Authority: EP
Inventors: Philip Frank French
Original assignee: Laing Orourke PLC
Current assignee: Laing Orourke PLC
Priority date: 2003-06-10
Filing date: 2004-06-03
Publication date: 2004-12-15
Also published as: GB2402698B; GB2402698A; GB0313368D0; EP1486629A3

Abstract

A fixing device (2) consists of a threaded rod (4) having tool engaging heads (8) at each end (6). The heads (8) have a maximum width which is smaller than the diameter of the rod (4). A nut (30) is fitted to the rod (4). The fixing device can be inserted from one side through a load limiting washer (26), an embedment (20) and into a threaded bore (12) in a shutter (10). After the concrete has been cast the rod (4) can be removed from the other side leaving the nut (30) in the concrete behind the embedment (20).

Description

Background of the Invention

The present invention relates to fixing devices and more specifically to devices for temporarily attaching embedments, such as local feature mouldings or permanent formworks otherwise known as plants, to shuttering.
Typically, features are created in the surface of cast concrete by attaching an appropriately shaped mould or plant to the inner surface of the shutter at the location of the feature. Such plants can be removed with the shuttering. If an item such as a channel, socket or other fixture is to be embedded into the concrete and left in place, it will be attached to the shuttering temporarily. Once the concrete has been cast the fixing devices used must be removed to enable the shutter to be removed leaving the embedment in place.
In practice embedments are normally attached to the shutter using a bolt or a machine screw which passes through the shutter and the embedment. The shutter and the embedment are then secured together using two nuts, a lock nut on the outside of the shutter, and a plain nut on the inner concrete side. The lock nut prevents the threaded end of the bolt passing too far through the nut on the embedment side and becoming bound up in the concrete. Once the concrete is set, the bolt, the lock nut and the shutter are removed leaving the embedment embedded in the structure together with the plain nut.
This process normally requires two workers, one on each side of the shutter. The shutters used can be very large and in order to avoid workers having to work in high places, the embedments are normally attached before the shuttering is erected. To do this the shutters may be laid on trestles to allow access to both sides. One worker will pass the bolt through a hole from below the shutter and the other will stand above it to attach the embedment and then tighten the plain nut. The two workers must communicate to ensure that the bolt does not protrude from the plain nut. The worker underneath the shutter tightens the lock nut against the shutter to ensure that the embedment is held in place securely. The process is labour intensive and time consuming especially if there are large numbers of embedments to be attached.
Alternatively embedments may be attached to the reinforcing bars in the concrete or, if the embedment is large, it may be held in place by a custom built frame. The problem with these methods is that they are time consuming and the embedments may not abut the shutters securely, which may result in a poor quality finish and the need for remedial work.
The demand for embedments to be cast into concrete during construction is increasing, as compliance with the health and safety regulations designed to reduce the risk of hard-arm vibration syndrome (HAVS), limits the use of percussive or vibrating drilling equipment on site to create fixings in the concrete after it has been cast.

Technical Problem

The present invention addresses the technical problem of providing a fixing device for the temporary attachment of embedments to shutters that can be installed and removed quickly and safely with the minimum labour requirement.

Prior Art Solutions

Other methods of temporarily attaching embedments to shutters have also been proposed such as magnets and suction cups. However, embedments secured by such methods are inherently prone to move during the concrete pour and subsequent vibration stage. The resulting feature may therefore be in an incorrect position and the movement may result in a poor quality finish which requires treatment with tools that are associated with a high HAV risk.
GB-A-2 145 460 (Rund-Stahl-Bau GmbH) suggests a fixing device that uses a vacuum pump to evacuate the air between the shutter and the embedment to create suction which holds the embedment in place. This method requires that the embedment should be air tight and would clearly be unsuitable for use with an embedment which runs the entire length of the shuttering such as a channel.

Solution of the Invention

The present invention accordingly provides a fixing device for attaching an embedment to a shutter, which has a threaded bore at a fixing position, the fixing device comprising a threaded rod having a first diameter sized to engage with the bore, the rod being provided at each end with a tool engaging head having a maximum width less than the first diameter; and a nut engageable with the threaded rod.
Preferably the threaded bore is formed in the body of the shutter by means of a threaded insert. Alternatively, the thread may be formed in a cavity behind the body of the shutter such as part of a flanged head threaded insert in a metal shutter.
The invention also provides a method of fixing an embedment to a shutter, the embedment defining an opening and the shutter having a threaded bore passing therethrough at a fixing position, comprising the steps of:
placing the embedment on a first side of the shutter with the opening aligned with the threaded bore;
assembling a nut of larger diameter than the opening to a first end of a threaded rod having a first diameter sized to engage with the bore, the rod being provided at each end with a tool engaging head having a maximum width less than the first diameter;
passing a second end of the threaded rod through the opening and screwing the rod into the bore by means of a tool attached to the head at the first end until the nut is against the embedment and that head has passed into the nut.
Using the device and method of the present invention a worker only requires access to one side of the shutter to fix the embedment. After the shutter has been erected and the concrete poured, the rod can readily be removed from the other, outer side of the shutter by means of a tool attached to the head at the second end.
The device and method are also advantageous as the fixing is self setting since a tool will automatically be disengaged from the head when the head enters the nut. The fixing can therefore be done quickly by relatively unskilled workers without the need for repeated setting-out.

Brief Description of the Drawings

In order that the invention may be well understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:

Figure 1: shows a perspective view of a fixing device of the present invention;
Figures 2A-E: shows a sequence of five diagrams showing an embedment being fixed to the shutter and the fixing device subsequently being removed; and
Figure 3: shows an obturator in position in a threaded bore in a shutter; and
Figure 4A-B: shows an alternative embodiment for the use of cavity type fixing in a metal shutter.

Detailed Description of a Preferred Embodiment

A fixing device 2 comprises an all threaded rod 4 having first and second identical ends 6. A hexagonal head 8 which has a maximum width smaller than a diameter of the rod 4 is provided at each end 6.
A shutter 10 which may be of steel or timber has a bore 12 at a desired fixing point for an embedment 20. In the embodiment described the embedment 20 is a channel intended to be cast into a surface so that other elements can be secured to the surface. It will be appreciated that other types of embedment can be fixed to a shutter 10 by the fixing device and method of the present invention.
The channel 20 has an opening 22 aligned with the bore 12. In practice, there will be a series of spaced openings in the rear wall of the channel each aligned with a respective bore 12 in the shutter 10.
Each of the shutter bores 12 is internally threaded. This can easily be achieved for a timber shutter by inserting a steel sleeve 24 threaded on both inner and outer cylindrical faces. Such an insert 24 is used in the furniture trade. These threaded inserts 24 can be installed in the shutter 10 in a workshop at the desired fixing locations. Therefore, the positioning is accurate.
Alternatively, the bores 12 can be created using a threaded insert 50 as shown in Figure 4A. The insert 50 is a metal component that has a flanged head 51 and a cylindrical body with a wider portion 54 adjacent to the head 51. The wider portion 54 has a smooth inner surface. A remote portion of the body has a threaded inner cylindrical surface 52. The insert 50 is inserted through the shutter 10 using a tool. The tool may be operated to deform the portion 54 in order to create a clamping flange 53 at the intersection between portions 52 and 54, like a rivet. Such a threaded insert 50 is particularly suitable for use with metal shutters but can also be used with timber shutters. Conventional cavity wall type fixings with a partially threaded inner cylindrical surface may also be employed as threaded inserts for timber shutters.
In order to fix the embedment 20 to the shutter 10, it is only necessary to have access to one side of the shutter. Therefore, it is not necessary to support on the shutter on trestles during the fitting operation and one worker can install the embedments.
A hexagonal nut 30 is screwed onto the rod 4. The diameter of the nut 30 is such that it will not pass through the opening 22 in the embedment. The length of the nut 30 is such that sufficient thread for its function remains after taking account of the loss of effective length caused by the engaging head 8.
A washer 26 is placed onto the rod 4 between the nut 30 and the opening 22 in the embedment. The washer 26 allows for variations in the size of openings 22 due to variations during manufacture. The washer 26 is compressible to provide a load limiting mechanism to avoid the assembly from locking up to such a degree that the nut 30 would need to be slackened off. A washer combination may also be employed.
Each of the tool engaging heads 8 of the rod 4 is designed to be engaged by a drill driver gun socket. It will be appreciated that heads of an appropriate form can be supplied for use with different tools. It is however essential that the head 8 should be smaller than the main body of the rod 4.
The rods 4 can be fabricated from zinc coated steel stud.

Installation

In order to fix an embedment 20 to a shutter 10, the nut 30 is assembled to a rod 4 adjacent to a first end 6 and then the other end is passed through a washer 26 and the opening 22 and into the bore 12. A drill driver tool (not shown) is coupled to the head 8 at the first end and used to drive the rod 4 through the threaded bore 24 as shown in Figure 2B. The head 8 at the second end of the rod helps engage the rod with the threaded bore. This is particularly useful for deep embedments 20.
The rod is screwed through the nut 30 and threaded bore 24 until the nut 30 is tight against the washer 26 and embedment 20 and the head 8 at the first end has passed into the nut 30. At this point the socket of the drill driver will automatically jump off the head 8. If the drill driver is provided with a torsion sensitive socket, it is possible to arrange for the driving tool to disengage before the screw of the rod and nut binds up. The use of a compressible washer 26 also prevents the nut 30 being overtightened. If a conventional drill is used to drive the rods into position either without a washer or with a non-compressible washer, it may be necessary to use a spanner to slacken off the nut 30 to release the tension slightly so that it is possible to remove the rod 4 later.
Once the embedments 20 have been securely fixed at all necessary fixing points to the shutter 10, the shuttering is assembled and the concrete poured. Once the concrete has cured the rods 4 of the fixing devices can be removed from the exposed face of the shutter 10 by engaging a tool with the head 8 at the second end of the rod 4. As the rod 4 is rotated it passes down through the nut 30 leaving the nut in position in the concrete and can be removed for reuse with a new nut 30.

Variations

A shearing element 40 may be chased out of the thread on rod 4 in order to enable the rod to be broken at an appropriate position within the embedment if the nut 30 becomes bound to the rod. A suitable position for the shearing element is illustrated at 40 in Figure 2D although this could be located at any position between the washer 26 and the face of the shutter 10.
Shutters may be provided with threaded bores at the required fixing positions. Since shutters are reused, there may be occasions where an embedment is not called for at a particular position. In this case it is necessary to fill the bore 12 in such a way that a feature is not created on the surface of the concrete. An obturator 42 with a large thin flexible head 44 can be used for this purpose. A rubber plug attached to a thin head is ideal as this can be readily located into the bore 12. It can be pulled out by gripping opposite sides of the flexible head 44. Such a obturator 42 could have a similar construction to a plug and patch device for mending punctures in motorcycle tyres. Reference may be made to CA-A-2375070 (42544563 Manitoban Limited) which describes such a patch plug in more detail.
The use of fixing devices as described reduces the need for additional finishing using vibrating tools and allows embedments to be rapidly and accurately positioned on a shutter with access to only one side.

Claims

A fixing device (2) for attaching an embedment (20) to a shutter (10), which has a threaded bore (12) at a fixing position, the fixing device comprising a threaded rod (4) having a first diameter sized to engage with the bore, the rod being provided at each end (6) with a tool engaging head (8) having a maximum width less than the first diameter; and a nut (30) engageable with the threaded rod (4).
A fixing device as in claim 1, wherein the threaded bore is formed in the shutter by means of a threaded insert (24).
A fixing device as in claim 1, wherein the threaded bore is formed outside the shutter in a projecting cylindrical body of an insert (50).
A fixing device as claimed in any one of the preceding claims further comprising a load limiting washer (20).
A method of fixing an embedment (20) to a shutter (10), the embedment (20) defining an opening (22) and the shutter having a threaded bore (42) at a fixing position, comprising the steps of:

placing the embedment (20) on a first side of the shutter (10) with the opening (22) aligned with the threaded bore (12);

assembling a nut (30) of larger diameter than the opening to a first end (6) of a threaded rod (4) having a first diameter sized to engage with the bore (12), the rod (4) being provided at each end (6) with a tool engaging head (8) having a maximum width less than the first diameter;

passing a second end of the threaded rod (4) through the opening (22)and screwing the rod into the bore by means of a tool attached to the head at the first end until the nut is against the embedment and that head (8) has passed into the nut.
A method as claimed in claim 5, wherein a load limiting washer (26) is placed between the embedment (20) and the nut (30).