GB2228439A - Method of producing tubular bodies - Google Patents

Description

1 1 IMPROVEMENTS IN AND RELATING TO TUBULAR BODIES This invention relates

to forming components including a generally tubular body. Tubular bodies of various cross- sections, for example round or rectangular are required for many industrial and domestic applications and are made by a number of different processes such as moulding, vacuum forming, roll forming and mechanical pressing. Although particular reference will be made in this specification to the production of, what in the art is called a cooking oven cavity, the underlying concept may be used for producing tubular bodies for other uses. A cooking oven cavity in accordance with the present invention may be used for both domestic and commercial/industrial cookers heated by gas or electricity.

Cooker oven cavities are usually made from sheet metallic material and comprise a tubular body of rectangular cross-section having one end (the back) closed and an opposite end (the front) open, to afford access into the oven cavity via a hinged door. It is known to produce grooves in each opposite and vertical side wall with each groove in one wall disposed parallel to a corresponding groove in the other wall for receiving an oven shelf. In section, when viewed from the front, the grooves are usually, but not necessarily, triangular in - 2 cross-section with the base of the triangle constituting an oven shelf support. Thus, when viewed from the front, each side wall of the oven cavity will resemble a series of saw teeth with the cross-sectional shape of the grooves affording access from the front enabling insertion and removal of the oven shelves. Conventionally, such sheet metallic cooker ovens are produced using the following sequential steps:- i) cut sheet to required size; ii) deform sheet material in a mechanical press against a former and in an inward direction considered relative to the internal cavity of a completed cooker. This results in all cases in the width across the f lat areas or faces of the vertical side walls being greater than the distances between the inward facing extremities of the shelf support grooves.

Deformation of the sheet to from the grooves causes unavoidable stress regions at those edges of the sheet in the region of the ends of the grooves resulting in turn, in buckling/ribbing due to material displacement during deformation.

It is, therefore, necessary to trim or otherwise remove the buckled and ribbed region prior to:

iii) folding the grooved sheet into a rectangular v) - 3 sectioned cavity; iv) the folded sheet is then welded or roll jointed and a back wall welded or roll jointed to the side walls; the so formed cavity is stove enamelled or otherwise treated with a self- cleaning composition and finally a frame hinge mounting units fitted for receiving a door.

It will be appreciated that trimming or removal of the buckled or ribbed region is not only time consuming but also wasteful of sheet material. It is an object of the present invention to reduce not only the extent of the deformed region caused by the buckling/ribbing but also the wastage of sheet material.

According to the present invention, forming at least one groove a method of extending generally longitudinally of a tubular body and opening into the interior of the body, wherein material from which the body is made is outwardly deformed against an outer former 20 defining a shape which corresponds at least to the shape of each groove, each groove terminating at least at one end thereof within the longitudinal extent of the body so as to leave a portion of the body undeformed. Preferably, the outer former is shaped to produce not only the shape of the 25 required groove or grooves but also the f inished cross- sectional and longitudinal shape of the body. Thus, where the method of the invention is used f or producing an oven cavity, the cross-sectional shape of the finished body will be essentially rectangular and the ends of the tubular body will be open. The grooves formed by outward deformation of a sheet metal tubular body will, in the case of an oven cavity be disposed in, what in use, will constitute side walls of the oven cavity and serve as guides or supports f or oven shelves. This allows f lat regions of the side walls to be left at a width less than the width across inward facing extremities of the shelf support grooves. Thus, features such as shelf stops (referred to hereinafter) can be readily integrated into the cavity side wall. The grooves may be of any desired cross-section such as, semi circular or resembling a right angled triangle. In the latter case, the base of the triangle will from a support for an oven shelf and the hypotenuse will extend upwardly to join the base of an adjacent triangular sectioned groove whereby the internal wall has a zig-zag or saw-toothed appearance.

In order to reduce the possibility of oven shelves supporting hot food, dishes etc being inadvertently removed from an oven, the grooves are conveniently formed with shelf stops. To this end, the grooves are preferably in two lengths spaced apart by an undeformed region for i 1 ns receiving a depending projection on the oven shelf. In such a construction, a user is required to displace the shelf slightly upwardly until the projection is disengaged from the undeformed region so as to permit removal of the shelf.

The existence of the undeformed region in a position along the length of the groove would, during normal pressing techniques, tend to produce not only regions of high stress but also a tendency to buckle or rib the surrounding area. Such tendencies are, however, considerably reduced using the method of the invention where the material of the tubular body is deformed outwardly, under pressure against the former. Preferably, deformation according to the present invention is performed using hydroforming techniques. Where indented, relieved, fielded or depressed regions are required in an oven cavity for housing heating elements, gas burners, fans, such regions can be formed simultaneously with the deformation of the grooves. In addition, those end regions to which a back panel and door frames are to be ultimately fitted and any additional reinforcement can also be formed simultaneously with the grooves.

The method of the present invention may be used for producing single oven cavities or two or more cavities in the end to end relationship from a single tubular body of any desired cross-sectional shape. Conveniently, the tubular body is of generally rectangular cross-section prior to hydrof orming. Where two or more cavities are formed from a single tubular body, all required deformation is carried in a single step and, therefore, the so formed cavity structure is divided as appropriate.

One form of cooker cavity in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 is a perspective of an oven cavity showing one side and the top of the cavity; Figure 2 is a perspective showing the cavity interior through that end which would,' in a complete c-:en, be enclosed by an oven door; Figure 3 is a perspective showing the exterior of the cavity from the rear and one side; Figure 4 is a side view taken from the opposite side of the cavity shown in Figure 1; Figure 5 is a rear view, and Figure 6 is a plan view, and Figures 7 and 8 show stages 1 and 2 in the hydro forming of the oven cavity of Figures 1 to 6.

Referring to the drawings, an oven cavity 1 made from sheet metal and of generally rectangular cross-section having a top wall 2, a bottom wall 3, two side walls 4 and 7 5, and a rear wall 6.

Each side wall 4 and 5 has a number of shelf supports 7 created by hydroforming the sheet metal into a series of panelled grooves or ribs 8. The ribs, see Figure 1 have a generally f lat region 9 and an inclined region 10. The f lat region 9 serves to support an oven shelf not shown. The ribs 8 are broken at 11, see Figures 1 to 4, dividing the flat region 9 into a short portion adjacent the front of the cavity and a longer portion extending towards the rear of the cavity. Cooker oven shelves frequently include a depending projection which is located in the break 11 to restrict fore and aft movement of the shelf within the oven. The break 11, constitutes a safety device to prevent removal of the shelf and hot food support therein unless a user raises the shelf to release the projection from the break.

It will be seen f rom the several Figures that the grooves or ribs 8 stop short of the cavity ends leaving a plain undeformed peripheral band 12. The plain undeformed peripheral band 12 serves to establish a surface against which the back 6 can be attached. The back 6 and the band 12 may be formed by roll forming or the back may be formed with a f lange permitting the back to be slid into the cavity from the rear and, thereafter, seam welded to the band as shown in Figures 5 and 6.

t Hinge mountings and/or door f rame supports may also be formed in that peripheral band 12 surrounding the cavity opening. Following completion of hydrof orming the cavity, the cavity is treated and finished using conventional stove 5 enamelling and self cleaning coating techniques.

Although in this specification, particular reference has been made to hydroforming oven cavities, the same techniques may be used f or f orming cylindrical drums used in laundry and tumble drying machines. Preferably, in the latter case, the grooves are f ormed to follow a helical path thereby assisting in agitation of the clothes during washing and drying. Further, the method described herein may be used f or forming any material capable of permanent plastic deformation, e.g. plastics materials.

Figures 7 and 8 shows stages 1 and 2 in the hydrof orming of the oven cavity 1. In Figure 7 a tubular body A of generally rectangular section is shown assembled over an inner f ormer B. The inner f ormer B includes a plurality of passages having an inlet Bl and outlets B2.

An outer f ormer 1 consisting of four parts of which two parts, namely, Cl and C2 are shown have, when assembled, a shape corresponding to the final external shape of the tubular body and each groove. In Figure 7 the two parts Cl and C2 are shown laterally displaced relative to the tubular body assembled over the inner former B. Each of X - 9 the two parts Cl and C2 include a groove G1 which corresponds to the shape of the shelf support grooves 8 of the oven cavity and a further cut out G2 serves to produce the break 11 (Figure 1) which constitutes a shelf stop.

Figure 8 shows the tubular body A clamped between inner and outer formers B and C after hydroformation of the cooker cavity, the arrows depicting the application of pressure applied at inlet B from an external source, not shown.

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Claims (12)

1. A method of forming at least one groove extending generally longitudinally of a tubular body and opening into the interior of the body, wherein material from which the body is made is outwardly deformed against an outer former defining a shape which corresponds at least to the shape of each groove, each groove terminating at least at one end thereof within the longitudinal extent of the body so as to leave a portion of the body undeformed.

2. A method of producing a tubular body including at least one groove extending generally longitudinally of the body with each groove opening into the interior of the body and terminating at least at one end thereof within the longitudinal extent of the body, the method comprising the steps of:

a) forming a tubular body of required length and cross-sectional shape from a deformable material; b) assembling the so-formed tubular body over an inner former defining a shape corresponding both to the shape of each groove and to the internal shape of the tubular body, the inner former including a plurality of passages with one or more inlets connectable to a source of pressure and having one or more openings which open into an external circumferential surface of the former and facing, when assembled, the interior of the tubular body; X_ c) locating the so-assembled tubular body and inner former within an outer former having a shape corresponding to a f inal external shape of the tubular body and each groove; d) sealingly clamping the tubular body between the inner and outer formers, and e) applying a source of pressure to the said one or more inlets of the inner former so as to outwardly deform the material of the body into conformity with at least the shape of each groove.

3. A method according to claim 2 wherein the tubular body is clamped in step (d) between the inner and outer formers in at least one region of the tubular body which is not deformed during step (e).

4. A method according to any one of claims 1, 2 or 3 wherein the tubular body is of substantially constant cross-section throughout the length thereof and the or each groove is\are disposed parallel to each other and parallel to a major longitudinal plane or axis of the body.

5. A method according to any preceding claim wherein that portion of the body which is undeformed constitutes a band extending around the periphery of the body.

6. A method according to any preceding claim wherein the tubular body is a cooker oven cavity of rectangular cross-section and the grooves constitute tracks for 1 1 - 12 receiving oven shelves.

7. A method according tb any preceding claim wherein the former has a shape corresponding to the finished shape of the oven cavity and formation of the cavity is performed 5 in a single step.

8. A method according to claims 6 and 7 wherein an oven back is attached to that part of the body in the region of the band.

9. A method according to any of claims 6, 7 or 8 10 wherein each groove terminates at each end thereof within the longitudinal extent of the body whereby those portions of the body which are undeformed constitute bands extending around the periphery of the body and at each end thereof.

10. A method according to claim 9 when the so formed body is divided longitudinally into at least two portions, each portion constituting a cooker oven separated by plain peripheral band.

11. A method according to claim 1 or claim 2 wherein the grooves follow a non-linear path.

12. A method according to claim 11 wherein the tubular body is cylindrical and the grooves follow a helical path.

Published 1990 a,ThePatentOlfice,StELte House. 6671 High Flolborn. London WC 1R 4TP. Further copies maybe obtLinedfrom The PatentOtfice Sales Branch, St Mary Cray. Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray. Kent. Con. 1 '87 1