GB2191968A - Shelf structure and method of making same - Google Patents

Abstract

A shelf 10, particularly for use in supermarkets, and having high load bearing capacity, has a shelf body member 14 and stiffening members 22, 24 secured to the underside of the body member by stud rivets 34. In manufacture, the shelf body member is precoated on its upper load bearing surface with a wipe-clean plastics material. The stud rivets are subsequently electrically welded to the underside of the pro-coated body member under conditions such that no significant damage to the surface finish of the plastics material occurs. The stud rivets are received in apertures in the stiffening members and subsequently formed with smooth heads. <IMAGE>

Description

1 GB 2 191 968 A 1

SPECIFICATION

Shelf structure and method of making same This invention relates to techniques for forfabricat- 70 ing metal structures, and is concerned specifically with the relatively narrowfield of fabricated shelf structures.

The applicants have considerable experience in the field of fabricated metal structures, such as sheet metal fabrications with which this application is principally concerned, and the techniques of sheet metal fabrication and the associated questions of the strength of fabricated structures and the suitability for such structures of thewide range of fastening techniques available for use are matters of everyday experienceto the applicants. Nevertheless,the specificfield of shelving with which this application is concerned, and in particularthe requirements of shelving for use in supermarkets, turns outto have rather specific and demanding technical parameters.

The structures and method of the present inven tion are applicable particularly, but not exclusivelyto shelving for use in supermarkets. In the case of sup ermarket shelves, there is a formidable list of techni cal requirements, amongstwhich are the following.

Firstly, there is the requirementfor strength. For ex ample, in the case of a shelf of length in the region of 1200 millimetres, it is necessaryforthe shelf to be able to carry a load of 300 kilograms. Such a load might arise when the shelf is stacked high with bags of sugar ortins of food. As a result of this require ment, some form of stiffening is needed forthe basic sheet metal body structure of the shelf. However, although the concept of stiffen ing such a shelf by fas tening to it one or more stiffeners appears to be a relatively straightforward matter, it does raise tech nical difficulties. Thus, for example, there is an inter action between the hyg iene and strength require ments of a supermarket shelf which raises g reat difficulties in relation to the methods of construction and surface finishes which can be adopted.

As regards the hygiene requirements, it is of cou rse vital in the case of a su permarket shelf that it can be f requently and easily cleaned, so that the food displayed is in a suitable environment. Such clean ing involves wiping the shelf surfaces with a suitably treated cloth orthe like. This must be done at short intervals of time. Moreover, it is importantthat dur ing the wiping operation, articles of dirt orfood etc can be completely removed and do not become lod ged in surface irregularities, edges, projections etc.

Thus, the surfacefinish of the shelf must be durable and wipe-clean and, even on the underside, the sur faces must be relatively smooth and free of dirt en trapmentzones.

As regardsthe durability of the surfacefinishes, we have discovered that a surface layer of a plastics material is particularly suitable. However, although no doubt it would be technically feasible to plastic coatthe product after fabrication, this is a relatively complex operation and the associated costwould be prohibitive for a product of this sortwhich is to used in high volume.

We therefore perceived that in orderto take advan- 130 tage of the good hyg ien ic qual ities of plastics-coated materials, itwould be necessaryto pre-coatthose materials in an economic manner before the fabrication process iscommenced. This howeverraises technical problems in relation to securing thestiffenerstothe shelf structure as mentioned above.

For example,the obvious andwell known techniques for securing togethersheet metal structures in a fabrication process, such as spotweiding or mechanical rivetting are obviously unacceptable. Spotwelding would obviously involve making electrical contact on both sides of the assemblyto befabricated and this would produce serious surface damage in the plastic-coated upper surface of the shelf.

This objection applies of course whetherthe shelf material is coated only on its upperside or on both sides.

Likewise, simple mechanical rivetting would result in, atthe very least, the presence of rivet heads at intervals along the plastic coated upper surface of the shelf.

Du ring the cou rse of an extended development programme we investigated the possibilities of employing a welding technique on the underside only of a shelf structure which is plastic-coated on its upper side. We discovered that it is possible to electrical ly weld to one side of a plastic-coated sheet without unduly damaging the plastic coating. However, the only immediately suitable technique for such welding, namely projection welding, proved technically inadequate. In short, underthe conditions of loading mentioned above, it wasfound that a significant proportion of the projection weldjoints failed when the shelf was loaded up to 300 kil- ograms.

An object of the present invention is to provide a shelf structure and a method of making same offering improvements in relation to one or more of the matters discussed above, or generally.

According to the invention, there is provided a method of making a loadbearing shelf structure, togetherwith a load-bearing shelf structure itself, as defined in the accompanying claims.

The invention also provides such a method and article not limited by all features of any particular claim herein, but comprising any novel feature or any novel combination of features disclosed herein.

An embodiment of the invention will now be described byway of examplewith referenceto the ac- companying drawings in which:

Figure 1 shows a section through a shelf structure, the section being taken at right anglesto the longitudinal direction of the shelf; Figure2 show a section through a second embodi- ment, the section being similarto Figure 1; and Figure 3 shows a side elevation view of an end portion of the shelves of Figures 1 and 2, the direction of viewing being shown by arrow Ill in Figures 1 and 2.

As shown in the drawings, there is provided a shelf structure 10 for use in a supermarket. The shelf is a fabrication formed from mild steel and, in this embodiment, is of length approximately 1200 millimetres and of width approximately 400 millimetres and has a load bearing capacity in excess of 300 kilograms. The shelf is formed with downwardly turned end 2 GB 2 191 968 A 2 flanges 12, one at each end of the shelf and exten ding across the full width of the shelf, for load bearing engagement with suitable shelf support brackets (not shown).

Shelf 10 comprises a shelf body member 14 having an upper load support surface 16.

Body member 14 has side flanges 18 formed with inturned edges 20.

Secured to the underside of body member 14 are two stiffening members. In the embodiment of Figure 1, the stiffening members 22,24 are of V section. In the embodiment of Figure 2 the stiffening members 26,28 are of so-called'top hat'section ie of rectangular channel section. In both the embodi merits of Figures 1 and 2,the stiffening members haveflanges 30,32 extending lengthwise of the stif fening memberand laterally outwardly from its edges and formed with spaced apertures inwhich fasteners34are affixed.

In use,the hollowsection stiffening members 22to 28 are securely held in position byfasteners34 againstthe substantial bending loads imposed thereon by merchandise carried on the shelves.

The structure and method of making the shelves 10will now be considered in more detail.

Shelf body member 10 is formed from a length of mild steel section having a coating of a plastics mat erial on its upper surface 16 and on the outer sur faces of side flanges 18 and inturned edges 20. The inner su rfaces of shelf body member 14 are coated with a weldable colour wash. Steel sections coated in this manner are obtainable from British Steel under the trade mark Stelvetite. Many other plastic coated steel and other materials may wel i be suitable forthe purpose of the invention. As regards the structure of 100 the body member, a variety of ferrous or otherweld able materials may be employed. As regards the plastics material, the main criterion is the possession of a durable wipe-clean surface which meets hygiene requirements and adheres satisfactorily to the mat erial of the body member. Possible examples are PVC, polypropylene, and many other synthetic poly mers and copolymers.

Stiffening members 22,24,26 and 28 are likewise plasticcoated on their outersurfaces in the same manner asthe shelf body member 14, and are mild steel sections.

Details of the manner of securing fasteners 34to the assemblywill now be considered.

Fasteners 34 are in fact stud rivets which are elec trically resistance welded to the underside 36 of the pre-coated body member 14 at spaced intervals. Dur ing welding, electrical connections to the shelf body member, forwelding purposes, are made solelyto the underside 36 orthe underside and the end 38 or side edges 40 of the body member. As welding pro ceeds, the conditions employed with respectto the time and temperature required for achieving a sat isfactory weld are chosen so as notto significantly damage the plastic upper surface f inish of the shelf body member 14. We have found that it is possible to achieve this desirable result without impairing the mechanical strength of the resu iting weld joint.

With the studs extending through the apertures formed in the flanges 30,32 of the stiffening mem- bers, all thatremains is to complete the fastening operation by provision of an end on the fasteners so as to secure the stiffeners in position.

We discovered, however, that conventional secur- ing means for stud fasteners such as plastic caps and nuts were not capable of meeting hygiene requirements and the ends of the stud fasteners were in stead formed with smooth domed heads 42 by a peening operation as a result of which the smooth slightly domed heads present a smooth surfacefor wipe-clean purposes and free of any significant dire entrapment zones. In the drawings, the heads of the fasteners are in some cases shown byway of iHustration, in a condition before completion of the peening operation.

After securing the stiffeners in position, all that remains is to surface treatthe underside of the shelf assembly as necessary. In the case wherethe stiffeners are themselves coated with plastics material, such surface treatment is only needed between the stiffeners and between them and the edge of the shelf assembly. Such surface treatment can, for example, be by means of painting. This underside, not being exposed to the abrasion and wearwhich occurs on the upper side of a shelf, does not necessarily require the plastics surface coating of the latter.

Among modifications which could be made in the above embodimentwhile remaining within the scope of the invention are the following:

1 The use for the shelf body member of a section which is pre-coated on both sides.

2 The use of alternative stiffening member sections. These need not necessarily be hollow sections.

3 The stud rivets may have tubular instead of solid shanks. This may require some modification of the end forming operation.

4 The sequence of operations need not necessarily be as described above. For example, the welding of the studs could be performed through the apertures in the stiffening members if necessary.

A variety of weldable structural materials may be employed together with a variety of plastics materials, as discussed above.

ltwill now be appreciated that amongstthe other advantages provided bythe embodiments described above is the simple fact of providing a heavyduty shelf with a pipe-clean plasticsurface. There has been a iongfeit need forsuch an article in super- markets despitethe existence for manyyears of all the materials needed forthe construction of such an article. We believe that we have explained abovethe reasons why conventional techniques have not hitherto produced a fabricated reinforced shelf structure having suitable wipe-clean characteristics. We also believe thatthe above embodiments represent a significant step forward in the art.

In this specification and claims the term'stud'may be used in stead of'stud rivet'since anysuitable form of stud maybe employed.

Claims (15)

1. A method of making load-bearing shelf struc- turecomprising:

3 GB 2 191968 A 3 providing a shelf body member having an upper load support surface; providing a stiffening memberforthe shelf body member; and securing thestiffening membertothe underside of theshelf body member so that the stiffening memberextends lengthwise of the body member; characterised in that the shelf body member is precoated on its upper load bearing surface with a wipe-clean plastics material; the method further comprising the steps of electricallywelding stud rivets to the underside of the pre-coated shelf body member at spaced intervals; the electrical connections to the shelf body member for welding purposes being made solelyto the underside of the shelf body member orthe underside and edges thereof; the conditions employed in welding the stud rivets to the shelf body member being such as notto significantly damage the surface finish of the plastics material on the load bearing surface of the shelf body member; the method further comprising the step of forming apertures in the stiffening member at intervals to receive the studs, and assembling the apertured stiffening member on the studs; and forming the ends of each stud so as to produce a smooth head thereon which is domed or convex, level orflat, or concave.

2. A method according to claim 1 wherein said stiffening member is of hollow section.

3. A method according to claim 2 wherein said hollow section is top hat section.

4. A method according to anyone of the preceding claims wherein said stiffening member is itself precoated with a plastics material.

5. A method according to anyone of the preceding claims wherein said stud rivets are solid stud rivets.

6. A method according to anyone of the preceding claims wherein the step of forming the ends of the studs comprises forming the studs with domed or slightly domed heads.

7. A method according to anyone of the preceding claims wherein said shelf member is precoated on its upper load bearing surface only, the method comprising the further step of surface treating the underside of the shelf member after assembly with the stiffening member.

8. A method according to anyone of the preceding claims wherein the shelf member has integral lengthwise side flanges which are plastic-coated.

9. A method according to claim 8 wherein said side flanges have inturned edges.

10. A method of making a load bearing shelf structure substantially as described herein with referenceto the accompanying drawings.

11. A load-bearing shelf structure made bya method according to any one of the preceding claims.

12. A shelf structure comprising a shelf body member having an upper load support surface and a stiffening member secured to the underside of the shelf body member and extending lengthwise thereof, characterised in that the shelf member is coated on its upper load bearing surface with a wipe clean pastics material, and said stiffening member is secured to the underside of the shelf body member by stud rivets electrically welded to the underside of the shelf body member at spaced intervals and extending through apertures formed in the stiffening member,the ends of the studs being formed so asto produce a smooth head.

13. A load bearing shelf structure substantially as described herein with reference to and as shown in the accompanying drawings.

14. A method of making a load bearing shelf structure comprising providing a shelf body member having an upper load support surface, providing a stiffening memberforthe shelf body member and securing the stiffening memberto the underside of the body member, characterised in thatthe stiffening member is secured to the shelf body member by stud rivets electrically welded to the underside of the body member at spaced intervals.

15. A load bearing shelf structure produced bya method according to claim 14.

Printed for Her Majesty's Stationery Office by Croydon Printing Company (L) K) Ltd, 11187, D8991685. Published by The Patent Office, 25 Southampton Buildings, London, WC2A l AY, from which copies maybe obtained.