GB2231819A

GB2231819A - Tubing manufacture

Info

Publication number: GB2231819A
Application number: GB8907509A
Authority: GB
Inventors: Phillip William Winfield
Original assignee: Glynwed Tubes and Fittings Ltd
Current assignee: Glynwed Tubes and Fittings Ltd
Priority date: 1989-04-04
Filing date: 1989-04-04
Publication date: 1990-11-28
Anticipated expiration: 2009-04-04
Also published as: IE901158L; GB2231819B; GB8907509D0; IE63276B1

Abstract

Tubing 1 having a hole 2 in its wall is manufactured by a continuous in-line process in which bar or strip is formed into the tubing which is finished to a required cross-sectional shape (eg. square, circular or rectangular) has the hole punched out of its wall and is cut to length. A wire hook can be attached at the hole 2 for the tubing to be suspended from a conveyor which takes the cut length of tubing through a paint spraying booth and drying oven. As illustrated, the hole is punched out by a lance blade 11 as the tubing is cut to length by a flying shear blade 3. The hole is diamond-shaped, the lance blade 11 having a tip (14, Fig 4) with a flat edge diagonally of the diamond and lengthwise of the tubing. The strip may be initially formed into round-section tubing by rolls. From the rolls, the tubing passes through an edge welding station, a flash removal dressing station, and then to further rolls which form the tubing to square section. As the shear blade 3 moves down, cam plates 9 cause dies 8 to move towards one another, to grip and support the tubing during cutting to length and hole punching. <IMAGE>

Description

IMPROVEMENTS RELATING TO TUBING MANUFACTURE This invention relates to the manufacture of tubing and more particularly tubing with holes in the walls of the tubing.

Continuous in-line manufacturing processes are known in which seamless or drawn tubing is continuously formed and runs on line straight to stations at which it is finished to a required cross-sectional shape and size and cut to desired lengths. Testing for integrity and size may also be carried out on the tubing before it leaves the line. The continuous process considerably increases production rates.

For the manufacture of products of various kinds in which tubing is used it is quite usual for the tubing to be pre-coated, for example by spraying or dipping. Again the coating and subsequent drying is conveniently done continuously. Commonly the tubing is carried suspended through a coating station and then through a drying oven. One way of attaching the tubing to the conveyor means from which it is suspended is by spring clips which grip inside the upper end of the suspended tubing. Because they can soon become damaged in the course of being inserted into the tubes anA by the heat conditions to which they are subjected, the clips have to be replaced regularly which makes their use expensive. An alternative is to attach wire hooks to the tubing which are suspended from conveyor means.

For the attachment of the hooks it is necessary for holes to be provided in the tubing.

Drilling holes into the tubing for the hooks can significantly reduce production rates and add to manufacturing costs. In the manufacture of electric resistance welded tubing from strip it has been proposed to provide slots in the strips before it is processed into the tubular form but the slots have tended to be distorted by the subsequent processing, which is unsatisfactory.

The present invention seeks to facilitate the provision of holes in tubing, particularly, though not exclusively, holes for the attachment of hooks to the tubing as aforementioned.

According to the present invention there is provided a continuous in-line process of manufacturing tubing in which bar or strip is formed into tubing, is finished to a required cross-sectional shape and size, has a hole punched out of its wall and is cut to a desired length.

The hole may be punched out of the wall as the tubing is cut to length. Conveniently the tubing is cut to length by means of a shearing blade and the hole is punched out as the shearing blade is operated. The hole may be punched out by a tool carried by the means which supports the shearing blade in its operation.

The tool may comprise a notching or lance blade.

Tubing of circular, square, rectangular or other shape in cross-section may be produced by the process.

As the hole is punched out of the tubing whilst the tubing is continuing in-line from the forming and sizing operations, it is formed without internal support being given to the wall of the tubing.

However, even though there is no internal support to help to take the impact of the punching tool on the wall it is possible to produce the hole with little or no deformation of the wall adjacent to the hole. The deformation can be reduced by suitable shaping of the tip of the punching tool. In a preferred form the tool produces a diamond-shaped opening and the tip of the tool presents a narrow flat edge across a diagonal of the diamond. Deformation can also be reduced by limiting the movement of the punching tool to no more than is necessary to form the hole, thereby minimising the extent of moving engagement, and drag, that the tool has with the wall of the tubing.Also when the tubing has a non-circular cross-section with corners it is preferred, whenever possible, to punch the hole through the wall at a corner because the angling of the wall towards the corner provides greater resistance to deformation under the impact of the punching tool.

Where the tubing is cut to length by a shearing blade it is usual for the tubing to be gripped between dies which give full peripheral support for the tubing as the shearing blade cuts through the tubing. This helps to resist deformation. The tubing may be similarly gripped in the region where the hole is to be punched out of the tubing. For the punching of a hole near to the cut end of the tubing the dies which grip the tubing for the cutting operation can also provide support for the tubing as the hole is produced. The hole should be spaced at least far enough from the end of the tubing for the material of the wall between the hole and the end to have sufficient structural strength to help in minimising deformation of the tubing as the hole is punched out of the wall.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a diagrammatic end view of tubing being cut to length and having a hole punched out of its wall; Figure 2 is a section on line 2 - 2 of Figure 1; Figure 3 is a front view of a lance blade used for punching the hole out of the tubing; Figure 4 is an enlarged inverted plan view of a tip of the lance blade; and Figure 5 is a perspective view of an end portion of a length of the tubing with the hole formed in it.

In this embodiment a process is provided for producing square-section steel tubing 1, as shown in Figure 5, for general purpose manufacturing use, including, for example, the manufacture of office and garden furniture and racking. The tubing 1 has a hole 2 punched out of its wall near one end so that for the purposes of pre-coating the tubing ready for its manufacturing use a wire hook may be inserted in the hole to suspend the tubing from a conveyor which carries the tubing through a paint spraying booth and a drying oven.

The tubing 1 is produced in a continuous in-line process. Steel strip drawn from a reel is passed through rolls which form the strip into a closed-jointed tube of round-section. From the rolls the formed tubing travels along a continuous feed track successively through a high frequency welding station, where abutting edges of the strip at the joint are welded together; a dressing station where external wall flash is removed from the tubing; a sizing station at which the tubing is accurately sized in the round form by finishing rolls and then by various breakdown rollers is progressively formed and sized to square section disposed with its diagonals respectively horizontal and vertical; a cutting and punching station where the tubing is cut into required lengths and a hole is punched through the wall of the tubing, and a testing station where the soundness of the welded joint is tested before each cut length of the tubing is removed from the feed track.

Cutting the tubing into lengths is done in a known manner by means of a flying shear blade in a pillar block 5 on the feed track. The shear blade 3 is bolted to, and depends from, a carrier 6 mounted on a powered ram, not shown, above the die set by which the shear blade is reciprocated vertically in the die set 4.

Die set 4 operates to grip and support the tubing as it is being cut. It comprises two pairs of dies 7, 8 respectively in front of and behind the shear blade 3, that is upstream and downstream of the shear blade with respect to the direction of travel of the tubing along the feed track. The dies of each pair move horizontally reciprocally towards and away from the tubing to grip and release the tubing. Cam plates 9 mounted on the carrier drive the dies of each pair, which are normally urged apart, towards one another as the shear blade is moved downwards to cut the tubing.

Each pair of dies 7, 8 defines a square-section passage 10 when the dies are closed together of complementary size to the external cross-section of the tubing and similarly disposed with the diagonals of the opening respectively horizontal and vertical. Thus the closed dies of the two pairs are able to grip and support the tubing all around its periphery in the passage 10, in front of and behind the shear blade.

Vertically movable with the shear blade 3 is a lance blade 11 which is bolted to the carrier 6 with the shear blade, by the same bolts. A packing block, not shown, spaces the lance blade 11 behind and in parallelism with the shear blade 3. The lance blade operates in a guideway 12 defined by the pair of dies 8 behind the shear blade and opening into the top carrier of the passage 10 in that pair of dies. The lance blade 11 is shorter than the shear blade and depends a shorter distance from the carrier.

Referring to Figures 3 and 4 of the accompanying drawings, the lance blade 11 has a lower end portion 13 which is narrowed down to a generally square cross-section with flattened corners and the diagonals of the square extending respectively parallel to and transversely of the width of the main body of the blade. The bottom of the lower end portion 13 is square cut to present a narrow elongated, flat tip 14 of the blade extending along the front-to-back diagonal of the square cross-section. At opposite sides of the tip the bottom is concavely radiussed down to the tip.

Typically the lance blade 11 has a thickness of 0.310" (8mm), the tip 14 is 0.310" (8mm) long and 0.0625" (1.6mm) wide, and the bottom of the lower end portion 13 has a 0.125" (3.2mm) concave radius down to each side of the tip.

For the cutting operation the dies 7, 8 of the die set are closed by the cam plate 9 to grip and support the tubing 1 as the shear blade begins to move downwards in its cutting stroke. Immediately after the tubing has been cut through and the shear blade approaches the end of its cutting stroke the lance blade, moving with the shear blade, punches through the wall of the severed length of the tubing at the top corner of the square cross-section, the tip 14 being presented lengthwise of the tubing along the corner.

The top enters only a short distance into the tubing before it retracts with the cutting blade. The dies open to release the tubing as the shear blade and lance blade complete the upward movement of their retracting stroke.

The hole 2 thus formed by the lance blade near the trailing end of the severed length of tubing is of diamond shape across the one corner of the wall of the tubing. Normally the slug of metal punched out of the wall by the lance blade is clipped away from the wall by the blade and falls inside the tubing. If it is not clipped way, which may happen as the tip 14 becomes blunted with use, the slug can be readily detached from the wall after the tubing has been removed from the feed track.

Typically the hole is formed approximately 0.75" (19mm) from the end of the severed length of tubing.

It has been found that in the forming of a hole in the manner described, using a lance blade of the form, and arranged, as described and illustrated, there is little or no noticeable deformation of the wall of the tubing caused by the punching operation.

Claims

1. A continuous in-line process of manufacturing tubing in which bar or strip is formed into tubing, is finished to a required cross-sectional shape and size, has a hole punched out of its wall and is cut to a desired length.

2. A process according to claim 1 in which the hole is punched out of the wall as the tubing is cut to length.

3. A process according to claim 2 in which the tubing is cut to length by means of a shearing blade and the hole is punched out of the wall as the shearing blade is operated.

4. A process according to claim 3 in which the hole is punched out by a tool carried by means which supports the shearing blade in its operation.

5. A process according to claim 3 or claim 4 in which the tubing is gripped between dies which give peripheral support for the tubing as the shearing blade cuts through the tubing.

6. A process according to any of claims 3 to 5 in which for the punching of the hole the tubing is gripped between dies in the region where the hole is to be punched out of its wall.

7. A process according to claim 6 as dependent from claim 5 in which the dies which grip the tubing to support the tubing as the shearing blade cuts through the tubing also grip the tubing in the region at which the hole is to be punched out of the tubing to support that region during the punching operation.

8. A process according to any preceding claim in which the hole is punched out of the tubing by means of a notching or lance blade.

9. A process according to any preceding claim in which the hole is diamond-shaped and produced by a tool having a tip which presents a flat edge across a diagonal of the diamond.

10. A process according to claim 9 in which the tool has an end portion of a generally square cross-section at which the tip is formed, being square cut to present the flat edge extending along a diagonal of the square cross-section of the end portion and being concavely radiused to the flat edge at opposite sides thereof.

11. A process according to any preceding claim in which the tubing is formed to a non-circular cross-section having a corner at which the hole is punched out of the wall.

12. A process according to claim 11 as dependent from claim 9 or claim 10 in which the flat edge at the tip of the tool is presented lengthwise of the tubing along the corner.

13. A process according to any preceding claim in which the tool by which the hole is punched out of the wall of the tubing is limited in its punching movement after contact with the wall of the tubing to substantially no more than is necessary to punch through the wall of the tubing to form the hole.

14. A process according to any preceding claim in which the hole is punched out of the wall of the tubing near to the end of the tubing at which the tubing is cut to the desired length.

15. A process according to any preceding claim including the further step of applying a coating to the tubing after it has been cut to the desired length, a wire hook being inserted in the hole whereby the tubing is suspended from conveyor means which carries the tubing through a paint spraying booth to apply the coating, and through a drying oven.

16. A process substantially as described herein with reference to the accompanying drawings.

17. A length of tubing having a hole in its wall manufactured by the process as claimed in any preceding claim.