GB2151523A

GB2151523A - Sheet metal articles

Info

Publication number: GB2151523A
Application number: GB08333620A
Authority: GB
Inventors: Arthur Edgar Carr; David Paul Erlam
Original assignee: Rittal Werk Rudolf Loh GmbH and Co KG
Current assignee: Rittal Werk Rudolf Loh GmbH and Co KG
Priority date: 1983-12-16
Filing date: 1983-12-16
Publication date: 1985-07-24
Also published as: DE8435956U1; GB8333620D0

Abstract

The article (20) has at least one edge folded at least once to form a reinforcement comprising a strip- like layer or layers (12) lying adjacent one side (14) of the sheet and a step (22) is formed in the sheet at a position inward of the edge such that the outer surface (24) of the reinforcement does not protrude beyond an outward projection of the surface of the side (14) of the sheet disposed inwardly of the step (22). <IMAGE>

Description

SPECIFICATION Sheet metal articles This invention relates to sheet metal articles.

It is often desired to reinforce and/or enhance the appearance of edges of articles made from sheet metal. This may be accomplished by fitting a separate reinforcement/embellishment member or edging strip to an edge of the sheet. For instance, it is known to form an instrument casing or the like from sheet metal and to fit a frame-like bezel to front edges of top, bottom and side portions of the casing to strengthen the casing and/or enhance its appearance.

Reinforcement and enhancement of the appearance of edges of sheet metal articles may also be accomplished by folding the edges. For example, an edge of a sheet metal article may be provided with a so-called "Dutch fold". That is to say, an edge of the article is folded or bent back to form a reinforcement which comprises a strip-like layer and which is disposed adjacent one side of the sheet. The fold hides the edge of the sheet to enhance the appearance thereof. In use, the sheet is orientated so that the side thereof to which the strip-like layer is adjacent is not visible or not readily visible. This can cause problems. For example, the strip-like layer protrudes (by an amount at least equal to its thickness) beyond the adjacent surface of the sheet. That is to say, there is in effect a discontinuity or step in the inner surface of the sheet.Consequently, in the region of this discontinuity the sheet cannot fit closely against some other surface, e.g. of a support structure, to which it may have to be attached. Further, if the sheet is used as a container or casing or the like to receive some object, the reinforced edge being around at least part of an opening in the casing or container, the strip-like layer restricts the size of the aperture. Thus, if the object is intended to be slid into the casing or container and is dimensioned so that it will just pass through the aperture, it will fit loosely in the container beyond the strip-like layer. Further, the discontinuity formed by the end edge of the strip-like layer can obstruct removal of the object in that the object can snag against it.

Another disadvantage of the Dutch fold technique is as follows. If a sheet metal article with a Dutch fold along an edge is to be bent at right angles to the edge, the reinforcement at the edge generally results in the radius of curvature differing as between the reinforced edge portion and the remainder of the sheet and/or in the formation of stretch marks at the juncture of the reinforced and non-reinforced regions of the bend. Such variation of the bend radius and/or stretch marks are generally perceptible and aesthetically unattractive.

According to the present invention there is provided a sheet metal article of which at least one edge is folded at least once to form a reinforcement which comprises at least one strip-like layer and which is disposed adjacent one side of the sheet, wherein a step is formed in the sheet at a position inward of said edge thereof such that the reinforcement does not protrude beyond an outward projection of that part of the surface of said one side of the sheet disposed inwardly of the step.

With such an arrangement, i.e. with an arrangement in which the reinforcement does not protrude beyond the adjacent part of the surface of the side of the sheet to which the reinforcement is adjacent, the part of the surface of said one side of the sheet can be positioned adjacent a support surface. Moreover, if the article is a casing or container and said edge is adjacent an aperture therein into which an object is to be inserted, the above structure should enable the object to fit closely in the container beyond the reinforcement and should minimise difficulty in removing the object.Furthermore, the step defines a distinctive and attractive raised or bezel-like edge portion of the sheet metal article which should enhance its appearance in a manner similar to that provided by a separate bezel member but without the extra step and possible extra cost of fitting such a separate bezel member thereto.

The sheet metal article may, if desired, be bent at at least one place about an axis perpendicular to said edge in such a sense that said one surface of the sheet is disposed inwardly of the bend. As for the case of a "Dutch fold" construction, as described above, it is possible that the radii of curvature of the bend may differ between the reinforced edge portion and the remainder of the sheet.

However, the discontinuity in the external surface provided by the step masks any such difference whereby the bend does not generally detract from the attractive appearance of the article. Also, the step should mask or avoid the occurrence of stretch marks.

The step is preferably so arranged that the reinforcement is flush with said outward projection of that part of the surface of said one side of the sheet disposed inwardly of the step. In this way, the surface of the side of the sheet to which the reinforcement is adjacent is substantially continuous or uninterrupted. This feature is of particular advantage where the article is to abut another surface both at the edge and adjacent the edge, or where the reinforced edge is provided around an aperture in a casing or container or the like into which an object is to be inserted and removed.

In one embodiment of the invention described hereinbelow, the reinforcement comprises a single strip-like layer which is disposed both adjacent and contiguous to said one side of the sheet. If, in this case, the reinforcement is to be flush with said outward projection of that part of the surface of said one side of the sheet disposed inwardly of the step, the height of the step will be equal to the thickness of the sheet. In other embodiments disclosed hereinbelow, the reinforcement comprises two or more strip-like layers formed by multiple folding or bending of the edge of the sheet.If, as is preferred, the different strip-like layers are contiguous with one another and with the said one side of the sheet, and the reinforcement is to be flush with said outward projection, the height of the step will be equal to the thickness of the sheet multiplied by the number of strip-like layers.

The sheet metal article can be of various kinds of metal. It can for example be of steel, aluminium or aluminium alloy.

An advantage of the present construction is that it is often possible to pre-coat the sheet metal (e.g. with paint or polyvinyl chloride), before the folding operation forming the reinforcement, without the coating being damaged in the folding process. Naturally, this can greatly simplify manufacture.

The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawing, in which like references indicate like items throughout, and in which: Figure 1 is an end view of an edge part of a sheet metal article showing a "Dutch fold" formed at the edge; Figure 2 is a partial perspective view of an article as shown in Figure 1 which has been bent about an axis perpendicular to the edge with a strip-like reinforcing layer of the Dutch fold on the inside of the bend; Figures 3 to 6 are views similar to Figure 1 of different forms of sheet metal article embodying the present invention; Figure 7 is a partial perspective view of an article formed by bending any of the articles of Figures 3 to 6 about an axis perpendicular to the edge thereof; and Figure 8 is a view of the structure of Figure 7 taken in the direction of an arrow VIII in Figure 7.

Figure 1 shows a sheet 10 of metal having a "Dutch fold" formed in an edge thereof.

Specifically, the edge is bent back or folded to form a reinforcement which comprises a striplike layer 12 and which is disposed adjacent and contiguous to a side 14 of the sheet.

The' 'Dutch fold" improves the appearance of the edge of the sheet 10 as viewed from the direction of an arrow 16 in Figure 1 in that the edge proper of the sheet 10 is not visible.

However, since the strip 12 is of unattractive appearance, the sheet 10 is generally so orientated in use that the side 14 is the inside thereof. As explained above, this can give rise to disadvantages. The discontinuity 18 in the surface of the side 14 at the end edge of the strip-like layer 12 means that the sheet cannot butt against another surface in the region of the discontinuity. Also, if the sheet 10 forms part or the whole of a casing or container or the like and defines the edge of an aperture into which an object is to be inserted, the strip-like layer 12 restricts the aperture size whereby something which can fit snugly into the aperture will fit loosely in the casing once it passes beyond the layer 12. Further, on withdrawal, the object could snag against the discontinuity 18.

It is known to form a box-like instrument casing by bending a sheet metal article 10 as shown in Figure 1. One or more of the articles 10 are bent about axes perpendicular to the illustrated edge so as to define top, bottom and side portions of the casing. Figure 2 shows one corner of such an instrument casing where an article 10 is bent through right angles about an axis 0-0 to form the illustrated corner. Apart from the disadvantages set forth above, such a structure is subject to the following further disadvantage. Obviously, there is a greater resistance to bending over the reinforced portion A of the bend than over the remainder B. This can detract from the aesthetic appearance of the casing, since the radii of curvature over the portions A and B can be perceptibly different and stretch marks can be formed in the sheet metal where the regions A and B blend with one another.

Figure 3 is a view, similar to Figure 1, of a first sheet metal article 20 embodying the present invention. The structure shown is generally similar to the "Dutch fold" of Figure 1, except that a step 22 is formed in the sheet 20 at a position inward of and closely adjacent to the reinforcement formed by the strip-like layer 12 such that the layer 12 does not protrude beyond an outward projection of that part of the surface of the side 14 of the sheet 20 disposed inwardly of the step. More specifically, in this embodiment, the outer surface 24 of the reinforcement is flush with an outward projection of that part of the surface of the side 14 of the sheet 20 disposed inwardly of the step 22. To this end, if, as illustrated, the strip-like layer is contiguous with the adjacent part 26 of the sheet 2a, the height of the step 22 will be substantially equal to the thickness of the sheet 20. The fact that the surface of the side 14 is therefore substantially continuous, right up to the edge, with the exception of a small recess 28, at least to some extent overcomes the disadvantages of the Dutch fold structure as described above with reference to Figure 1.

Further embodiments of the invention will now be described with reference to Figures 4 to 6, which will be described only in so far as they differ from the embodiment of Figure 3.

In Figure 4, the edge of the sheet 20 contains two folds or bends such that the edge reinforcement comprises two like strip like layers 12 which are contiguous to one another and to the part 26 of the sheet 20. In this case, the height of the step 22 is twice the thickness of the sheet 20.

In each of Figures 5 and 6 the edge of the sheet 20 contains three folds or bends so that the reinforcement comprises three like striplike layers 12 which are contiguous with one another and with the part 26. In these cases, the height of the step 22 is substantially equal to three times the thickness of the sheet 20. The structures of Figures 5 and 6 differ from one another as regards the folding technique employed. In Figure 5, the strip-like layers 12 form, together with the part 26, a generally spiral configuration. In Figure 6, the thickness of the sheet metal is first bent double and the doubled thickness is then bent again so that only two folding operations are necessary to form the three folds or bends. It is believed that formation of the structure as shown in Figure 6 will therefore generally be simpler than formation of the structure shown in Figure 5.

As will be evident from the foregoing, similar embodiments with more than three striplike layers can be formed in generally similar manner.

The step 22 in the embodiments of Figures 3 to 6 may be of a variety of forms. Preferably, however, it is formed as shown, that is to say the sheet 20 is bent in two places so as to form an inclined substantially straight portion that joins the part 26 of the sheet 20 and the remainder of the sheet. The angle of inclination is not believed to be critical. However, it is convenient, as shown in Figure 6, for the angle of inclination to be equal to 45 .

Sheet metal articles 20 as described with reference to Figures 3 to 6 can be used in a variety of applications. They can for example be used as panels or doors for cabinets or casings for housing instrumentation or other electrical/electronic apparatus. Such a panel may for example comprise a flat, square or rectangular member with edge formations as described formed along at least one edge thereof, and preferably along at least two opposed edges thereof. Such panels would usually be arranged with the sides 14 thereof on the inside so that the raised edge portions thereof would provide an attractive bezel-like appearance rather like that which would be provided if separate bezels or edging strips were fitted thereto.

By way of example, structures like those shown in Figures 3 to 6 can be formed from 22 SWG or 0.7 mm mild steel and the widths of the strip-like layers 12 may be in the region of 18 mm. However, other materials (e.g.

aluminium or aluminium alloy) or other dimensions may be employed. Further, as indicated above, at least the side of the sheet 20 opposite to the side 14 may be pre-coated with paint or polyvinyl chloride or some other coating material prior to the edge folding operation, which can considerably simplify manufacture. A manufacturer may, for example, produce the article 20 from boughtin pre-coated material.

The sheet metal articles 20 described with reference to Figures 3 to 6 may also be bent to form various items such as parts of metal furniture or parts of instrument casings or cabinets. To this end, the article 20 may be bent at at least one place about an axis perpendicular to the edge illustrated in Figures 3 to 6 in such a sense that the reinforcement constituted by the strip-like layer or layers 12 is on the inside of the bend. A part of such a structure is shown in Figures 7 and 8, the axis of a bend being shown at 0-0 in Figure 7. Naturally, the stiffened or reinforced edge will have a greater resistance to bending than the remainder of the article 20 whereby the radii of curvature may differ between the reinforced region A and the nonreinforced region B of the bend. However, by virtue of the discontinuity in the outer surface provided by the step 22, any such difference between these two regions is masked or hidden by the step 22 which"marries" the regions A and B.

Further, the step 22 should serve also to discourage the occurrence of or hide any stretch marks appearing at the junction of the regions A and B. In summary, the structure of Figures 7 and 8 should serve at least partially to overcome the aesthetic disadvantages of the "Dutch fold" structure, when bent, as described above with reference to Figure 2.

Claims

1. A sheet metal article of which at least one edge is folded at least once to form a reinforcement which comprises at least one strip-like layer and which is disposed adjacent one side of the sheet, wherein a step is formed in the sheet at a position inward of said edge thereof such that the reinforcement does not protrude beyond an outward projection of that part of the surface of said one side of the sheet disposed inwardly of the step.

2. A sheet metal article according to claim 1, bent at at least one place about an axis perpendicular to said edge in such a sense that said one surface of the sheet is disposed inwardly of the bend.

3. A sheet metal article according to claim 1 or claim 2, in which the step is so arranged that the reinforcement is flush with said outward projection of that part of the surface of said one side of the sheet disposed inwardly of the step.

4. A sheet metal article according to claim 1 or claim 2, in which the reinforcement comprises a single strip-like layer which is disposed both adjacent and contiguous to said one side of the sheet.

5. A sheet metal article according to claim 4, in which the height of the step is equal to the thickness of the sheet so that the reinforcement is flush with said outward projection of that part of the surface of said one side of the sheet disposed inwardly of the step.

6. A sheet metal article according to claim 1 or claim 2, in which the reinforcement comprises two or more strip-like layers formed by multiple folding or bending of the edge of the sheet.

7. A sheet metal article according to claim 6, in which the different strip-like layers are contiguous with one another and with the said one side of the sheet, and the height of the step is equal to the thickness of the sheet multiplied by the number of strip-like layers so that the reinforcement is flush with said outward projection.

8. A sheet metal article according to any one of the preceding claims, formed of steel, aluminium or aluminium alloy.

9. A sheet metal article according to any one of the preceding claims, which was precoated before the folding operation forming the reinforcement.

10. A sheet metal article substantially as hereinbefore described and illustrated with reference to Figures 3 to 7 of the accompanying drawing.