GB2063735A - Method of forming projections on sheet metal - Google Patents

Abstract

Projections 19 are formed on sheet metal by rolling between two rolls having respective peripheral formations, each of which includes, as viewed along the axes of the rolls, two involute curves 14, 15. <IMAGE>

Description

SPECIFICATION Method of forming projections on sheet metal and roll for use in the method This invention relates to the forming of projections on sheet metal.

Pieces of sheet metal having on one face rows of projections commonly used in flooring and other situations where the sheet metal will be walked on. The projections are intended to reduce the risk of the person's feet slipping on the sheet metal.

The term "sheet" is not used herein to designate metal having a thickness within a particular range or to differentiate from metal strip. Pieces of sheet metal to which the invention is applied will generally be cut from coiled metal strip. The pieces of sheet metal may have peripheral flanges or be otherwise formed to a non-flat cross section.

The usual way of forming projections on pieces of sheet metal at the present time is by a pressing operation. In a case where elongate pieces of sheet metal are required to be formed to have a channel-shaped cross section and outwardly directed projections on a mid-portion of the section, strip metal stock is passed continuously between pairs of forming rolls to bend lateral portions of the stock out of the plane of the major part of the stock to form side limbs of the channel and successive lengths of the channels are then subjected to a pressing operation between male and female dies having respective formations which cooperate with the metal to produce the required projections.

It will be appreciated that the conjunction of a continuous rolling process with an intermittent pressing operation is inconvenient. Nevertheless, up to the present time, there has been no satisfactory alternative to the pressing operation for forming the projections.

We have previously attempted to form projections on sheet metal by passing the sheet metal between a pair of driven forming rolls, these rolls having formations similar to those provided on the known press tools. This attempt was unsuccessful for a number of reasons. There was excessive resistance to movement of the sheet metal along the feed path between the rolls. The speed of the sheet metal between the rolls tended to be less than the speed at which the material was fed towards the rolls, with a consequent tendency for the sheet metal to buckle at the infeed side of the forming rolls. As a leading end portion of each piece of sheet metal passed between the rolls there was an excessive load on the motor driving the rolls. The forming rolls were deflected from their required positions and tended to come out of mesh. This resulted in breakage of the formations on the rolls.The projections produced by the forming rolls on the sheet metal were not evenly distributed although the formations were evenly distributed on the forming rolls. Furthermore, the formation produced on the sheet metal did not have the required symmetrical shape although the shapes of the formations on the forming rolls were symmet- rical. Attempts to compensate for the lack of symmetry by providing asymmetrical formations on the forming rolls failed.

We have now discovered that the foregoing problems can be substantially overcome by providing on the forming rolls formations having a profile, as viewed along the axes of the rolls, which includes two involute curves arranged symmetrically about a diametral plane of the corresponding roll to provide a constant gap between respective formations of the forming rolls which are in mesh with one another.

According to a first aspect of the invention, there is provided a method of forming projections on a piece of sheet metal wherein the piece of sheet metal is passed between a pair of rolls having at their circumferences respective formations which engage opposite surfaces of the sheet metal, the rolls are rotated about respective parallel axes, the formations on one roll push the sheet metal into gaps between adjacent formations on the other roll and said formations have a profile, as viewed along the axes of the rolls, which includes two involute curves arranged symmetrically about a diametral plane of the corresponding roll.

The formations of one of said rolls, for convenience called herein the male roll, preferably have a dimension extending parallel to the axis of the roll which is less than the corresponding dimension of the formations on the other of said rolls, for convnience called herein the female roll.

Each formation of the female roll and each gap between adjacent formations thereof may extend from one end of the female roll to the other end.

The male roll may push the sheet metal further into certain parts of each gap than into other parts or push the sheet metal only into certain parts of each gap.

The sheet metal may be pierced by some of said formations when it is pushed into said gaps or into some of said gaps.

The formations of the male roll may be arranged in rows which extend along the roll with the length of row parallel to the axis of the roll. Alternatively, the formations of the male roll may be arranged in helical rows around the axis. The formations on the female roll may also be of helical form.

According to a further aspect of the invention there is provided a roll for use in the method of the invention, the roll having on its peripheral surface a plurality of rows of projections, there being a plurality of projections in each row and each projection having a profile, as viewed along the axis of the roll, which includes two involute curves arranged symmetrically about a diametral plane of the roll.

An example of a method embodying the first aspect of the invention and in which there is used a roll embodying the second aspect of the invention will now be described, with reference to the accompanying drawing wherein Figure 1 shows sheet metal passing between a pair of forming rolls viewed along the axes of the rolls, and Figure 2 shows a perspective view of the rolls and material emerging from between the rolls.

The apparatus used to perform the method illustrated in the accompanying drawing includes a male forming roll 10 and a female forming roll 11 mounted in a supporting structure (not shown) for rotation about respective axes which are parallel to each other.

The female roll 11 has on its periphery a series of formations 12, each in the form of a tooth which extends without interruption from one end of the roll to the other end and is parallel to the axis of the roll. Between each pair of adjacent teeth 12 there is a corresponding gap 13 which also extends without interruption from one end of the roll to the other end. The cross section in a plane perpendicular to the axis of the roll of each tooth 12 is uniform along that tooth and is such that the profile of the tooth includes first and second convex involute curves, 14 and 15, disposed symmetrically about a diametral plane 16 of the roll 11. The form of the female roll 11 is identical with that of an involute spur gear.

The male forming roll 10 has on its periphery a plurality of rows of formations, each in the form of a tooth 17. Each row extends along the roll from one end thereof to the other and is parallel to the axis of the roll.

Each row comprises a plurality of teeth 17 with spaces 18 between them. Thus, the dimension of each tooth 17 which extends parallel to the axis of the roll is considerably less than the corresponding dimension of each tooth 12. The profile of each tooth 17, as viewed along the axis of the roll 10 is identical with that of the teeth 12 on the roll 11.

The male forming roll 10 may be produced by producing a roll identical with the female forming roll 11 and then cutting a plurality of grooves around the periphery of the roll to provide the spaces 18. Thus, the rolls 10 and 11 have the same diameter, teeth of the same profile in a plane perpendicular to the roll axes and teeth at the same pitch. If required, rolls having the same diametral pitch but different overall diameters may be used.

The profile of the teeth 17 as viewed in a direction transverse to the axis of the roll 10 may be similar to the profile as viewed along the axis. The surfaces of a tooth 17 which face adjacent spaces 18 may be curved or flat and converge towards each other in the radially outward direction. The radially outermost surfaces of the teeth may form respective parts of a cylindrical surface coaxial with the roll.

During use, both of the rolls 10 and 11 are driven. Sheet metal on which projections are to be formed is fed towards the nip between the rolls so that respective surfaces of the sheet metal are engaged by the teeth 1 2 by the teeth 1 7. 'he teeth i 1 push coro- sponding oars of the sheet metal onto the qaps 13 betweer the teeth 12 to form projections 1 9 occupying these gaps.

The rolls 10 and 11 are supported in such position that the involute surfaces of a tooth 17 which proiect into a @ap 13 are spaced from the involute surfaces of the teeth 12 on opposite sides of the gap 13 by a distance substantially equal to the thickness of the sheet metal. This spacing remains substan- tially constant as a particular tooth 17 rnoes into and out of mesh with teeth on the roll 11. The sheet metal is thereby gripped securely between the rolls 10 and 11 and is not free to slide over the surface of the teeth.

With the male forming roll 10 above the female forming rolls, as shown in Fig. 1, projections are formed on the underside of the sheet metal. Proiections can be formed on the upper surface of the sheet metal it the forming rolls are interchanged.

We have found that bv means of the rolEs illustrated in the accompanying drawings, projections can be formed on sheet steel with the projections having a substantially symmetrical shape, being evenly distributed over the surface of the sheet steel and with all projections on the piece of sheet steel having substantially the same shape. Furthermore, we have found that, if the piece of sheet steel is flat prior to entry between the roils 10 and 11, the generally flat confiauration is not dis- turbid by the action of the rolls.

The accompanying drawings illustrate the formation of projections or sheet metal without piercing of the sheet meal. If reaIiire(, the rolls may be arrangea' to pierce the s--sc- metal in each projection. To effect piercing, there are provided on the forming rolls some what larger teeth similar to the teeth 12 and 1 7 but at a larger pitch. The large, teet@ on the male forming roll penetrate further into the gaps between the teeth ot the female roil than do the teeth 1 7. This penetration of the larger teeth is sufficient to pierce the sheet metal n each prcjection. The resulting free edges of metal further reduce the risl: of footwear slipping on flooring formeri of the pierced sheet metal.

In the particular sramole iCustrated in the accompanying drawings. each row of teeth 17 is arranged parallel to the axis of the roll 10 and the corresponding projections are formed concurrently. Alternatively, each row of teeth on the male forming roll may be arranged as a helix around the axis of the roll. The corresponding projections would then be formed sequentially. Depending upon the pitch of the teeth, successive teeth in a helical row may enter successive gaps 1 3 in the female forming roll. However, we prefer that if helical rows of teeth are provided on the male forming roll then each tooth on the female forming roll should be of corresponding helical form.

Claims (9)

1. A method of forming projections on a piece of sheet metal wherein the piece of sheet metal is passed between a pair of rolls having at their circumferences respective formations which engage opposite surfaces of the sheet metal, the rolls are rotated about respective parallel axes, the formations on one roll push the sheet metal into gaps between adjacent formations on the other roll and said formations have a profile, as viewed along the axes of the rolls, which includes two involute curves arranged symmetrically about a diame tral plane of the corresponding roll.

2. A method according to claim 1 wherein the formations of one of the rolls have a dimension extending parallel to the axis of the roll which is less than the corresponding dimension of the formations on the other of the rolls.

3. A method according to claim 2 wherein each formation of said one roll and each gap between adjacent formations thereof extends from one end of the roll to the other end.

4. A method according to claim 3 wherein said other roll pushes the sheet metal further into certain parts of each gap in said one roll than into other parts.

5. A method according to claim 3 wherein said other roll pushes the sheet metal only into certain parts of each gap between the formations of said one roll.

6. A method according to claim 4 or according to claim 5 wherein the sheet metal is pierced by some of said formations when it is rushed into said gaps or into some of said gaps.

7. A roll for use in a method according to any preceding claim, the roll having on its peripheral surface a plurality of rows of projections, there being a plurality of projections in each row and each projection having a profile, as viewed along the axis of the roll, which includes two involute curves arranged symmetrically about a diametral plane of the roll.

8. A method of forming projections on a piece of sheet metal substantially as herein described with reference to the accompanying drawing.

9. Apparatus substantially as herein described with reference to and as shown in the accompanying drawing for forming projections on a piece of sheet metal.

1 0. Any novel feature or novel combination of features disclosed herein or in the accompanying drawing.