GB2257062A - Forming an elongate metal member. - Google Patents

Abstract

Roll-formed metal tube having a row of apertures along its length is formed by piercing flat stock 10 to form the apertures 13 but then returning the slugs to the apertures before the stock is roll-formed to the required cross sectional shape. The slugs are ejected from their apertures after the tube has been formed. <IMAGE>

Description

Title: Method of forming an elongated, metal member and apparatus for use in the method Description of Invention The present invention relates to a method of forming an elongated metal member having a transverse cross section which includes a bend or more than one bend and a row of apertures spaced from each other along the member.

It is known to form members of this kind from imperforate, strip metal stock by forming the stock into a tube or other member having the required transverse cross section and subsequently piercing the required apertures in the formed member. In a case where the member is a tube, it is usual to join opposite edges of the stock to each other in the formed tube. This may, for example, be achieved by welding the edges to each other. Piercing the apertures in the formed tube is inconvenient and limits the rate of production.

We have attempted piercing the apertures in the strip metal stock whilst the stock is in a substantially flat condition and subsequently forming the pierced stock into a tube. However, we have discovered that this procedure suffers from the serious disadvantage that the deformation of the stock which is necessary to form the tube deforms the material bordering the apertures so that the apertures in the finished member do not have the same shape as the apertures which are initially pierced in the stock. Furthermore, faces of the formed member have undulations which impair the appearance of the member.

According to a first aspect of the present invention, there is provided a method of forming an elongated metals member having a non-rectilinear transverse cross section and a row of apertures spaced from each other along the member, wherein each of said apertures is formed by punching a slug of metal at least partly from the metal stock, each slug is returned to the corresponding aperture, the stock is then formed to the required cross sectional shape and the slugs are then removed from their apertures.

We have found that the presence of the slugs in the apertures during forming of the stock to the required transverse cross sectional shape enables deformation of the material to be controlled so that apertures of a required size and shape can be achieved in the final member without piercing in the stock apertures which differ significantly from the apertures required in the finished member. The improved control over deformation of the material also mitigates the problem of undulations impairing the appearance.

The initial punching of the slugs of metal from the stock may be performed in a press. Conveniently, a number of slugs are punched concurrently from a part of the stock and the stock is then advanced through the press, in preparation for the punching of a number of slugs from an adjacent part of the stock.

The slugs may be returned to the corresponding apertures by the action of one or more rolls, past which the stock is moved or by the action of the press.

Punching of each slug from the stock is preferably performed by moving a punch into engagement with a face of the stock and then moving the punch through a part only of the thickness of the stock.

According to a second aspect of the invention, there is provided apparatus for use in a method according to the first aspect and comprising a press having punches for punching the slugs from the stock, a plurality of sets of rolls for forming the stock to the required cross section and ejectors for ejecting each slug from the formed member.

An example of apparatus embodying the second aspect of the invention and which is used in performance of a method according to the first aspect of the invention will now be described, with reference to the accompanying drawings, wherein: FIGURE 1 illustrates diagrammatically metal stock subjected at various positions along its length to different steps in the method, FIGURE 2 illustrates a cross section through punch and die tools in a press, together with a portion of stock operated upon by the tools and a pair of rolls operating upon an adjacent part of the stock, and FIGURE 3 shows a part of Figure 2 on a larger scale, and FIGURE 4 illustrates a later step in manufacture of the apertured member.

The method illustrated in the accompanying drawings is used to form from flat, strip metal stock 10 tube having a rectangular transverse cross section and two rows of apertures extending along the tube. In the example illustrated, the apertures are all rectangular and have the same size and shape. It will be understood that the method may be used to form apertures of different sizes and shapes. Also, in the member illustrated, the apertures are in the minor faces of the tube. The method could alternatively be performed to provide apertures in one or both major faces of the tube. It will also be appreciated that the method could be used to form a member having a non-rectilinear transverse cross section which is other than a rectangular tube.

The stock 10 is passed, in a substantially flat condition between tools of a set of tools mounted in a press in a known manner. The set of tools comprises a number of punches, one of which is identified by the reference numeral 11, and a die 12 having respective cavities suitable for receiving the punches. Preferably, each of these cavities contains a block 23 of an elastomeric material covered by a rigid cover 24 (not shown in Figure 2) which maintains the block in a compressed condition and which, when the punches are raised, has a face flush with the face of the die 12 which is presented towards the punches.

The working face of each punch has substantially the size and shape of the apertures which are required to be present in the finished tube. In the present example, the punches are arranged in two rows, corresponding to the rows of apertures 13 to be formed in the stock. The punches 11 are carried in a common carrier 14 which is mounted in a fixed position relative to the die 12 and is spaced therefrom by a distance substantially greater than the thickness of the stock 10.

When a part of the stock which is to be worked by the punches 11 is drawn into the gap between the press tools, the stock rests on the die 12 and the punches are retracted into the punch carrier 14. The punches are then driven by the press into contact with a face of the stock 10 and movement of the punches towards the die 12 is continued until each punch has penetrated a predetermined distance into the stock 10. This distance is a proportion only of the thickness of the stock but is preferably more than 50% of the thickness of the stock and is preferably less than 90% of the thickness of the stock. Penetration of each punch into the stock causes a corresponding slug, one of which is identified by the reference numeral 15, to be punched partly out of the stock to leave therein a recess 16.The slug enters the corresponding cavity in the die 12 and compresses the block of elastomeric material therein. The punches do not enter the cavities of the die 12.

When the punches have penetrated the predetermined distance into the stock 10, movement of the punches is reversed and the punches are withdrawn into the punch carrier 14. This raises the stock into engagement with the punch carrier, before continued movement of the punches strips the stock from the punches. Movement of the stock into engagement with the punch carrier 14 withdraws the slugs from the cavities of the die 12 and this is assisted by expansion of the elastomeric material in the die cavities. The gap between the punch carrier 14 and the die 12 is sufficient to accommodate the stock and the slugs protruding therefrom, so that the punch carrier and die do not interfere significantly with advancement of the stock from the press tools towards the rolls 17 and 18 illustrated in Figure 2. These rolls are positioned downstream of the press and act on the partly-pierced stock to drive the slugs 15 into the recesses 16 so that the overall thickness of the stock is returned to its initial value.

During the pressing operation, the metal at the periphery of each slug may be ruptured so that each slug becomes a piece of metal separate from the stock 10 and held in the stock by mechanical interference. Alternatively, rupturing of the metal at the periphery of each slug may be only partial so that there remains a continuous connection between each slug and the stock. This connection would extend through only a part of the thickness of the stock.

To ensure the maintenance of a continuous connection between each slug and the stock, the die 12 may be relieved locally as shown at 19 in Figure 3.

The relief shown at 19 has the form of a tapered notch cut in the boundary surface of the die cavity adjacent to the working face of the die. The or each notch extends around only a small proportion, for example 1% or 2%, of the periphery of the die cavity. When the punch drives the slug partly into the die cavity, material at the periphery of the slug is deformed to occupy the notch 19 and this avoids complete rupturing of the metal in the vicinity of the notch.

After the stock has passed through the nip defined by the rolls 17 and 18, it is passed through a number of sets of forming rolls which progressively form a stock into the required tube. Suitable arrangements of forming rolls and their use are well known. After forming into the tube, abutting edges may be joined to each other by welding or in some other way. For example, mutually interfitting formations may be formed on opposite edges of the stock 10 during the pressing operation and brought into interfitting relation as the tube is formed, so that these formations hold the edges together in the completed tube.

After the tube has been formed to the required cross section, it is passed between a pair of rolls 20 and 21 which bear on opposite, minor faces of the tube. Each of the rolls 20 and 21 is equipped with a number of ejectors 22 arranged in a row around the periphery of the roll. Each ejector has a size and shape, as viewed in a direction towards the axis of rotation of its roll, corresponding to the size and shape of the slugs 15. The ejectors are biased towards respective positions in which they protrude from the peripheral surface of the roll and, during movement of the formed tube between the rolls 20 and 21, the ejectors engage corresponding slugs and push the slugs out of the apertures in the tube wall to the interior of the tube.Engagement of successive ejectors with the tube at the boundaries of the corresponding apertures causes the rolls 20 and 21 to turn in synchronisation with movement of the tube between the rolls.

The rolls may be driven by movement of the tube between the rolls or torque may be applied to the rolls in a known manner, -additionally to driving by means of the tube, the action of the tube on the ejectors being relied upon merely to maintain synchronisation.

The ejectors 22 are biased to the positions in which they protrude from the periphery of the corresponding roll and are so mounted that they can be depressed into the roll, for example in the event of an ejector engaging a portion of the tube which does not have a correctly positioned slug and corresponding aperture to receive the ejector.

There is no support inside the tube at a position between the rolls 20 and 21. The force which must be exerted by the ejectors 22 on each slug 15, in order to push the slug from its aperture in the tube, is small, as compared with the force which must be exerted on the blank by each punch 11 to form the slug.

The action of the ejectors on the slugs does not deform the tube, notwithstanding the absence of internal support for the tube.

The roll-forming line may operate continuously, drawing stock at a steady rate from a loop of stock between the press and the roll-forming line. The press delivers stock to the loop intermittently. Alternatively, the stock could be stored in coils after punching and before forming.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (9)

1. A method of forming an elongated metal member having a nonrectilinear transverse cross section and a row of apertures spaced from each other along the member, wherein each said aperture is formed by punching a slug of metal at least partly from the metal stock, each slug is returned to the corresponding aperture, the stock is then formed to the required cross sectional shape and the slugs are then removed from their apertures.

2. A method according to Claim 1 wherein each slug is returned to the corresponding aperture by the action of one or more rolls, past which the stock is moved.

3. A method according to Claim 1 or Claim 2 wherein, to punch the slug partly from the stock, the stock is engaged by a punch and the punch is moved through a part of the thickness of the stock.

4. A method according to Claim 3 wherein the punch pushes the slug into a female die.

5. A method according to Claim 4 wherein the female die is relieved at one or more positions around the periphery of the slug and the material of the stock adjacent to the slug at this position or each of these positions is deformed but is not completely severed from the slug until after the stock has been formed to the required cross sectional shape.

6. A method according to any preceding claim, wherein, during removal of the slugs from their apertures, no extraneous support is applied to the surface of said member where the slug are expelled from their apertures.

7. Apparatus for use in a method according to Claim 1 and comprising a press having punches for punching the slugs from the stock, a plurality of sets of rolls for forming the stock to the required cross section and ejector means for ejecting each slug from the formed stock.

8. A method substantially as hereindescribed with reference to the accompanying drawings of forming an elongated metal member having a nonrectilinear transverse cross section and a row of apertures spaced from each other along the member.

9. Any novel feature or novel combination of features disclosed herein or in the accompanying drawings.