GB2148758A

GB2148758A - Bending mandrel

Info

Publication number: GB2148758A
Application number: GB08329194A
Authority: GB
Inventors: Mansell Thomas Gowing
Original assignee: Norcros Investments Ltd
Current assignee: Norcros Investments Ltd
Priority date: 1983-11-02
Filing date: 1983-11-02
Publication date: 1985-06-05
Also published as: GB2148758B; GB8329194D0

Abstract

A metal extrusion of generally channel section can be bent to a required profile by the insertion of a plurality of laminae (12) which together correspond to the internal profile of the section to be bent. The laminae are held together at one end by a pin (14) to which is attached an elongate member and after the bend has been formed the laminae are withdrawn by any suitable means. <IMAGE>

Description

SPECIFICATION Bending Laminae This invention relates to a tool to enable bending of generally square or rectangular section hollow members.

The problem of bending pipes and tubes has long since been overcome by the provision of special spiral springs which are inserted into a tube to be bent and then withdrawn by axial force after the bending operation has been completed. The withdrawal of the bending tool can sometimes require substantial force but is automatically assisted because the axial force applied to the spring automatically gives rise to a radial contraction. Even if some crinkling of the tube results, this is generally of no importance from the appearance point of view although it may be inconvenient from the point of view of increasing the internal resistance to flow.

With hollow members of non-circular section and especially box sections, the problem of bending without permitting the appearance of crinkles or creases becomes rather more acute since obviously a spiral spring type of bending tool cannot be employed and the use of particulate matter such as sand contained within the hollow member by end plugs has the substantial disadvantage that involves, for each operation substantial expenditure of time and no guarantee of a satisfactory result. If the end plugs are not secure the compaction of the sand or other particulate matter will not be maintained and crinkles or creases will then certainly arise.

Aluminium and light alloy extrusions are frequently employed in the construction of glazed structures such as greenhouses and glasshouses but acute design limitations arise because it is essential that only rectilinear parts shall be used. If extruded members are not used the only alternative is cast structures which generally involve greater expense and cannot conveniently be made of aluminium or light alloy which has many advantages from erection and structural standpoints.

According to the present invention there is provided a tool to enable a length of extruded at least substantially closed, non-circular, section extruded member to be bent, the tool comprising a plurality of laminae held together by securing means at one end only and together forming a cross-sectional profile closely matched to the internal profile of the member to be bent, and having a length corresponding to the portion of the member to which a bend is to be applied.

Further, according to the present invention, there is provided a method of imparting to a hollow generally closed section metal member a desired curvature comprising the steps of inserting a tool in accordance with the immediately preceding paragraph, applying a bending stress to the member and after achieving the desired curved shape, withdrawing the tool by pulling axially on the tool at the end thereof where the laminae are secured together.

A bending tool embodying the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawing in which: Figure 1 is a perspective view of a typical tool in accordance with the invention; Figure 2 is a longitudinal section through a length of member to be bent with the tool of Figure 1 in position ready for the bending operation; and Figure 3 is a longitudinal section of the member of Figure 2 afterthe bending operation has been completed.

Referring now to Figure 1, the tool 10 of which a typical example is illustrated comprises a plurality of metal laminae 12 for example, of stainless steel, with the individual laminae carefully dimensioned so as to match, overall, the cross-section of the member to be bent at any given location. At one end only, the laminae are secured together by a bolt or pin 14, the ends of which will be countersunk to avoid interference with the side wall of the member to be bent. In orderto minimise frictional forces when it is necessary to withdraw the tool after a bending operation, the individual laminae will be coated with a lubricant over the areas of contact.

As illustrated in Figure 2, the member 15 to be bent is initially rectilinear and the tool, attached to a suitable flexible member such as a wire strand 16 is inserted until it reaches the length at which the bend is required. The bending operation is then completed on the conventional bending jig to the required curvature and, as illustrated in Figure 3, the laminae will no longer be aligned at the free ends. In order to remove the tool, the member is securely clamped and the elongate flexible member 16 is attached to a winch (not shown) in order to enable withdrawal. The lubricant applied assists in this operation but as will be understood particularly where aluminium or light alloy sections are involved, the relatively harder stainless steel of the laminae will totally exclude the possibility of creases or crinkles arising thus simplifying the withdrawal operation.

1. A tool to enable bending a length of an extruded, at least substantially closed, non-circular, hollow section member, the tool comprising a plurality of flexible laminae held together by securing means at one end portion only and together defining an external cross-sectional profile closely matched to the internal cross-sectional profile of the member to be bent, the laminae having a length corresponding to at least the length of the member to which a bend is to be imparted.

2. A tool for bending a length of an extruded, at least substantially closed, non-circular hollow section member, the tool comprising a pack of flexible laminae having an external cross-sectional profile substantially corresponding to the internal cross-sectional profile of the length to be bent, a rivet passing through the pack at one end portion and having attached thereto an elongate flexible member enabling the laminae to be drawn through the hollow section to be bent.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Bending Laminae This invention relates to a tool to enable bending of generally square or rectangular section hollow members. The problem of bending pipes and tubes has long since been overcome by the provision of special spiral springs which are inserted into a tube to be bent and then withdrawn by axial force after the bending operation has been completed. The withdrawal of the bending tool can sometimes require substantial force but is automatically assisted because the axial force applied to the spring automatically gives rise to a radial contraction. Even if some crinkling of the tube results, this is generally of no importance from the appearance point of view although it may be inconvenient from the point of view of increasing the internal resistance to flow. With hollow members of non-circular section and especially box sections, the problem of bending without permitting the appearance of crinkles or creases becomes rather more acute since obviously a spiral spring type of bending tool cannot be employed and the use of particulate matter such as sand contained within the hollow member by end plugs has the substantial disadvantage that involves, for each operation substantial expenditure of time and no guarantee of a satisfactory result. If the end plugs are not secure the compaction of the sand or other particulate matter will not be maintained and crinkles or creases will then certainly arise. Aluminium and light alloy extrusions are frequently employed in the construction of glazed structures such as greenhouses and glasshouses but acute design limitations arise because it is essential that only rectilinear parts shall be used. If extruded members are not used the only alternative is cast structures which generally involve greater expense and cannot conveniently be made of aluminium or light alloy which has many advantages from erection and structural standpoints. According to the present invention there is provided a tool to enable a length of extruded at least substantially closed, non-circular, section extruded member to be bent, the tool comprising a plurality of laminae held together by securing means at one end only and together forming a cross-sectional profile closely matched to the internal profile of the member to be bent, and having a length corresponding to the portion of the member to which a bend is to be applied. Further, according to the present invention, there is provided a method of imparting to a hollow generally closed section metal member a desired curvature comprising the steps of inserting a tool in accordance with the immediately preceding paragraph, applying a bending stress to the member and after achieving the desired curved shape, withdrawing the tool by pulling axially on the tool at the end thereof where the laminae are secured together. A bending tool embodying the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawing in which: Figure 1 is a perspective view of a typical tool in accordance with the invention; Figure 2 is a longitudinal section through a length of member to be bent with the tool of Figure 1 in position ready for the bending operation; and Figure 3 is a longitudinal section of the member of Figure 2 afterthe bending operation has been completed. Referring now to Figure 1, the tool 10 of which a typical example is illustrated comprises a plurality of metal laminae 12 for example, of stainless steel, with the individual laminae carefully dimensioned so as to match, overall, the cross-section of the member to be bent at any given location. At one end only, the laminae are secured together by a bolt or pin 14, the ends of which will be countersunk to avoid interference with the side wall of the member to be bent. In orderto minimise frictional forces when it is necessary to withdraw the tool after a bending operation, the individual laminae will be coated with a lubricant over the areas of contact. As illustrated in Figure 2, the member 15 to be bent is initially rectilinear and the tool, attached to a suitable flexible member such as a wire strand 16 is inserted until it reaches the length at which the bend is required. The bending operation is then completed on the conventional bending jig to the required curvature and, as illustrated in Figure 3, the laminae will no longer be aligned at the free ends. In order to remove the tool, the member is securely clamped and the elongate flexible member 16 is attached to a winch (not shown) in order to enable withdrawal. The lubricant applied assists in this operation but as will be understood particularly where aluminium or light alloy sections are involved, the relatively harder stainless steel of the laminae will totally exclude the possibility of creases or crinkles arising thus simplifying the withdrawal operation. CLAIMS

3. A method of imparting to an extruded hollow, generally closed section, metal member, a desired curvature, comprising the steps of inserting a tool in accordance with claim 1 or claim 2 into said member, applying a bending stress to the member and, after achieving the desired curvature, withdrawing the tool by pulling axially of the tool at the end thereof where the laminae are secured together.

4. A bending tool substantially as hereinbefore described with reference to the accompanying drawings.

5. A method of imparting to a hollow generally closed section member a desired curvature substantially as hereinbefore described with reference to the accompanying drawings.