GB2244016A

GB2244016A - Bolt

Info

Publication number: GB2244016A
Application number: GB9011111A
Authority: GB
Inventors: Paul R Raybone
Original assignee: LEADA ACROW
Current assignee: LEADA ACROW
Priority date: 1990-05-17
Filing date: 1990-05-17
Publication date: 1991-11-20
Anticipated expiration: 2010-05-17
Also published as: GB9011111D0; GB2244016B

Abstract

A bolt 2 is made by tapping a threaded hole 10 in a first rod 4, welding the first rod coaxially at 8 with a second rod 6 and arming a thread 12 on the free end of the second rod. The bolt thus formed comprises two welded parts, a first part having a threaded hole extending along the length thereof and the second part having an external thread at its free end. <IMAGE>

Description

Title IM,9h: 'E. TN AND A T I 0 Ti EL - This invention relates to bolts employed in formwork and in particular to bolts employed to connect a structural formwork member to a rod.

One type of bolt which is commonly used in formwork has a first end formed with an internal threaded hole and a second end formed with an external thread. The bolt can be passed through a structural member and be secured at its first end to a rod which is threaded along its length, or at least at its ends, by screwing an end of the rod into the first end of the bolt. A nut could be mounted on the second end of the bolt to hold it in position on the structural member. If the free end of the rod is secured, for example connected to another such bolt positioned through a second structural member, then the first structural member can be pulled towards the rod by tightening up the nut.

One common usage is in the production of walls where the panels, between which the wall is to be formed, are supported by beams, a rod being mounted between the beams by use of two bolts of the type described above which are passed through the beams in the panels. The nuts and the bolts are tightened to pull the panels hard towards each other to resist the forces experienced as the wall is formed. When the wall is set the bolts are withdrawn by unscrewing them from the rod which is left within the wall.

The small holes left by the first ends of the bolts can be filled.

This type of bolt is commonly known as a "she bolt".

One known method of forming a she bolt is simply to blind tap a threaded hole in one end of a section of rod and tap an external thread into the other end. The problem with this method is that blind tapping only allows production of small pitch threads on the internal hole.

Thus she bolts formed by this method cannot be employed with large pitch threaded rods.

An alternative method which does permit the formation of an internal hole with large pitch threads is to tap a thread through the whole length of a piece of rod and then attach one end of the rod to an externally threaded second rod. The rods have to be connected by crimping an end of the first rod around an end of the second rod as welding damages the second rod. The disadvantage of this is that the bolt produced is not strong and has been found to tend to break, ie seperate into its two parts, particularly on withdrawal of the bolt in the wall forming method described above.

Despite many efforts no satisfactory method of forming a bolt for use with threaded rods with a large pitch thread has been found.

In accordance with the invention a method of forming a bolt of the type having a first end formed with a threaded hole and a second end formed with an external thread comprises tapping a threaded hole through the length of a first rod, welding the first rod coaxially with the second rod and forming a thread on the free end of the second rod.

Preferably the two rods are welded together by friction welding.

A bolt of the type having a first end formed with a threaded hole and a second end formed with a external thread in accordance with the invention comprises a first rod formed with an internal threaded hole extending along the length thereof and a second rod, substantially longer than the first rod, having at one end thereof an external thread formed on the surface thereof, the other end of the second rod being welded to an end of the first rod.

The bolt is capable of use with any type of threaded rod no matter what the pitch of the threads is.

Furthermore it is sufficiently strong that it will not break when withdrawn from the edges of a wall. The bolt has been found to work extremely well in practice.

Preferably the first rod is tapered from the end connected to the second rod to the free end thereof. This facilitates removal of the bolt from a formwork arrangement. The end portion of the second rod may also be lapered to given a longer "nose" and further facilitate removal of the bolt.

Suitably the extreme end of the threaded end of the second rod is machined into a square to provide a grip surface for a spanner again to facilitate removal of the bolt from a formwork arrangement.

The invention will now be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a side view of a bolt in accordance with the invention and Figure 2 is a schematic view of a formwork arrangement employing a pair of bolts as shown in Figure 1.

The bolt 2 comprises two portions 4 and 6 connected by welding (see dotted line 8). Portion 4 is tapered from the end connected to portion 6 to its free end and has an internal threaded hole 10 extending through the length thereof. The free end of the portion 6 is threaded, see 12, but the extremity thereof is machined to form a square 14 whereby the end can be gripped by a spanner. A hexagonal nut 16 is provided for the bolt 2 and a waler plate 18 may also be screwed onto the threaded end of the second portion 6.

The bolt 2 is manufactured by firstly taking a relatively short piece of hexagonal or round bar and drilling and tapping centrally down the length of the bar to provide a threaded internal hole along the length thereof. This first piece of the bar which forms portion 4 is then fiction welded to a second piece of bar of substantially greater length very preferably by friction welding. The second length of bar forms the portion 6.

The assembled unit is then machined to give a tapering nose at the end with the internal hole. The first portion 4 may solely be tapered or, to provide a longer nose, the whole of the portion 4 and part of the portion 6 can be tapered. The non-tapered end is then machined to give an external thread and a square is machined at the extremity thereof. This square 14 allows a spanner to be used with the bolt 2.

A hexagonal nut is then tapped with the same thread as provided at the non-tapered end of the bolt and is screwed onto the bolt at the threaded end thereof.

Figure 2 illustrates one use of the bolt 2. In this arrangement a wall is to be formed in the region 20 between two panels 22, each panel being supported by a structural member 24, for example a soldier, and bracing members 26. A bolt 2 is passed through each structural member 24 and its associated panel 22 and a threaded rod 28 is connected between the bolts 2 by screwing its ends into the internal hole 10 at the tapered end of the bolts 2.

The connection is tightened up by turning the nut 16 on the bolt 2 which forces the waler plates 18 hard against the structural members 24 and thus pulls the structural members closer together. Concrete or other building material is then filled into the region 20 around the rod 28. Once this is set the bolts are withdrawn by applying a spanner to their square ends 14 and turning this to cause the bolt 2 to unscrew from the rod 28. The rod 28 is left in the wall and the small holes produced in the wall as a result of the tapered bolt heads can be filled in.

The bolt 2 can be employed with any rod no matter what the pitch of the thread is on it. It is strong and does not have a tendency to break on withdrawal from a wall or other structure. The method of manufacture allows production of a bolt with any required size internal hole thread.

Claims

1. A method of forming a bolt of the type having a first end formed with a threaded hole and a second end formed with an external thread comprising: tapping a threaded hole through the length of a first rod, welding the first rod coaxially with a second rod, and forming a thread on a free end of the second rod.

2. A method as claimed in Claim 1 wherein the two rods are welded together by friction welding.

3. A bolt of the type having a first end formed with a threaded hole and a second end formed with an external thread comprising: a first rod formed with an internal threaded hole extending along the length thereof, and a second rod, substantially longer than the first rod, having at one end thereof an external thread formed on the surface thereof, the other end of the second rod being welded to an end of the first rod.

4. A bolt as claimed in Claim 3 wherein the first rod is tapered from the end which is connected to the second rod to the free end thereof.

5. A bolt as claimed in either Claim 3 or Claim 4, wherein the free end portion of the second rod is tapered.

6. A bolt as claimed in any one of Claims 3 to 5, wherein the extreme end of the free end of the second rod has a square cross-section.

7. A method of forming a bolt substantially as hereinbefore described and illustrated in the accompanying drawings.

8. A bolt substantially as hereinbefore described and illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows 1. A method of forming a bolt of the type having a first end formed with a threaded hole and a second end formed with an external thread comprising: tapping a threaded hole through the length of a first rod, welding the first rod coaxially with a second rod, and forming a thread on a free end of the second rod.

3. A bolt formed by the method of either Claim 1 or Claim 2.