GB2173728A - Method and apparatus for cold rolling malleable metallic strip - Google Patents

Abstract

Apparatus for rolling malleable metal strip into tapered or trapezoidal cross-section includes a pair of inclined rollers 2,3 and a guide plate 31 for defining the plane of and providing a reaction support for the deeper side of the strip. The guide plate assists in maintaining the strip straight downstream of the rollers, and is preferably scalloped to accommodate the rollers and may be adjustable to allow for a different width of copper strip. <IMAGE>

Description

SPECIFICATION Method and apparatus for cold rolling malleable metallic strip This invention relates to cold rolling a strip of malleable metal to a tapered, preferably trapezial cross-section. The invention is particularly concerned with rolling copper strip of rectangular section to a strip of trapezial cross-section suitable for commutator segments in electrical motors or other dynamo electric machines.

It is usual practice, in the production of copper strip in trapezoidal form, to define the thickness and the width of the strip by means of either a die or a plurality of orthogonally arranged rollers, known as turkshead rollers. In practice such methods require a comparatively large number of passes through the rollers or through sets of rollers to achieve the required form, usually require annealing of the strip, and are expensive.

It is known from British Patent Specification No.

791401 to provide, in a hot rolling process, a guide plate upstream from a pair of mutually tapered rollers for the purpose of guiding a strip of metal between the rollers.

According to the invention, apparatus for cold rolling malleable strip into tapered cross-section comprises a pair of rollers, means for setting the rollers at a relative angle defining the taper of the cross-section, and a static guide which extends downstream from the rollers and defines a datum for the wider side edge of the strip. The static guide, which is preferably adjustable to permit selection of different widths of strip, assists in maintaining the strip straight downstream from the rollers.

Preferably the static guide is in the form of a plate of which a narrow side face defines the said datum. Such a plate is easy to position, support and replace. The plate is preferably located between the rollers and may be scalloped in its broad faces for the accommodation of the rollers. This enables the rollers to be positioned very close to the guide plate yet permits adjustment of the plate into and out of the space between the rollers without danger of engagement between the plate and the rollers. The plate may include a guide member positioned for the support of an underside of the strip and extending downstream along part of the said side face of the plate. This provision assists the maintenance of the strip in the correct position relative to the rollers. Moreover, the strip may be supported above a deck so as to provide a space into which swarf may fall.Preferably a shaver is disposed to trim the narrower edge of the strip.

The shaver is preferably located in a fixed position defining a datum plane for the narrower side of the strip, the width of which is determined by the positioning of the static guide plate. The deck may include a recess accommodating a removable post that supports the underside of the strip at a location spaced from the aforementioned guide member. Such a post is useful for providing support after the position of the rollers for the underside of comparatively wide strips.

The invention includes within its scope a method of cold rolling a strip of malleable metal into tapered cross-section, comprising passing the strip through a pair of rollers which are set at an acute angle defining the taper of the cross-section and supporting the thicker side of the strip after the rollers by means of static guide. As will become apparent, according to one preferred feature of the method, the cross-section of the strip is altered from substantially rectangular to a required section by means of a single pass through the pair of rollers.

One example of the invention is described hereinafter with reference to the accompanying drawing, in which: Figure 1 is a simplified general view of a machine embodying the invention; Figure 2 illustrates a pair of forming rollers and various devices associated therewith; Figure 3 mainly illustrates a static guide plate in plan view; Figure 4 is a side view of the guide plate; Figure 5 is a simplified diagram of part of a machine embodying the invention; and Figure 6 is a sectional view through a trapezoidal strip shown in conjunction with the guide plate and other components.

In Figure 1 is illustrated a frame 1 in which are mounted two forming rollers 2 and 3 between which the copper strip is to be drawn. The rollers are driven by respective motors (not shown) in known manner and are adjustable to vary their mutual inclination as shown in Figure 2. Preferably the lower roller has a fixed horizontal axis and the upper roller has an axis of which the inclination may be adjusted. A malleable metal strip, which is normally copper but may be of other malleable metals or alloys, is drawn between the rollers in a manner described hereinafter. Upstream of the rollers is a guide assembly illustrated schematically at 5 receiving the strip 4 from a source, usually a coil of copper strip, the direction of movement of the copper strip being shown by the arrow 6.

The upper roller 3 has a central portion 3a and two tapered end portions 3b. The lower roller 2 has a central portion 2a, a right-hand tapered portion 2b and a left-hand portion comprising two portions 2c and 2d of successively greater taper.

The additional taper 2c allows the rolling of thin sections without changing the datum position for the thin edge.

Downstream from the rollers, the leading end of the strip 4 is engaged by a clasp 7 mounted on a carriage 8 which may include a load cell for monitoring the tensile load applied to the strip 4 by the carriage. A hook 10 is engageable with a link of a draw chain 11 extending between spaced apart wheels 12 and 13 respectively remote from the close to the frame 1. A motor 14, controlled by the load cell 9, drives the chain 11 in a direction to draw the carriage 8 away from the frame 1. Preferably the motor 14 maintains the pull on the strip constant.

The motor 14, the chain 11 and the carriage 8 constitutes a draw bench of generally known construction. Other means may be used for drawing the strip between the rollers but a draw bench is preferable.

The strip 4 is drawn between the rollers until the carriage 8 approaches the far end of the draw bench, near roller 12, whereupon the hook may be disengaged from the chain in response to a signal from the sensor (not shown) in the proximity of the carriage to the far end of the draw bench.

As shown in Figure 2, the roller 2 is horizontal and is mounted in bearing assemblies 21 and 22.

The roller has an extension shaft carrying a drive flange 23 driven by means of a universal coupling from an electric motor (not shown). The roller 3 likewise has bearing assemblies 24 and 25 and a drive flange 26 which is driven by a respective universal coupling from a respective motor (not shown).

The bearing assemblies 24 and 25 are supported in respect of yokes 27 and 28. The verticai positions of the yokes may be adjusted by screw jacks 29 and 29a respectively, which may be driven by a respective motor Only the motor 30 for the screw jack 29 is shown. However, the yoke 27 is similarly movable. The yokes 27 and 28 are adjusted in position in order to set the mutual inclination of the rollers 2 and 3 in accordance with the desired taper of the trapezoidal cross-section of the strip.

Extending partly between the rollers 2 and 3 and both upstream and downstream therefrom is a guide plate 31 which may abut a fixed part of the frame 1. By means of spacing blocks the extent to which the plate 31 extends into the spacer between the rollers may be adjusted, as is schematically shown by the double headed arrow 33.

The plate 31 constitutes a static guide and reaction member for defining the position of the thicker edge of the copper strip 4. It also assists in keeping the strip straight, inhibiting its tendency to curl. As is shown in Figures 3 and 4, the plate 31 in its upper and lower broad faces respectively has an upper scallop, which is tapered to accommodate the inclined upper roller 3 and a lower scallop 36, which may be of constant width, accommodating the lower roller 2. The scallops permit the close approach of the rollers and the close consignment of the strip. In general, the same guide plate may be used for strips of different width and of different taper but it may be preferable to employ plates of different thickness according to the desired maximum thickness of the tapered copper strip.

However, one of the advantages of the invention is the ease with which one guide plate can be exchanged for another of different thickness.

The plate 31 may include a tungsten carbide insert 31a to provide a hard wearing face in the region against which the strip 4 is forced.

Figure 3 illustrates the use of spacing blocks 34 abutting the fixed member 32 which is part of the frame 1.

Preferably a guide member in the form of a ridge extends along part of the narrow face of the guide plate 31. The purpose of this ridge 38 is to support the underside of the strip and thus assist the maintenance of the strip in correct position relative to the rollers 2 and 3. The guide ridge extends from a position preferably close to the rim of the lower scallop 36.

As is shown in Figure 5, the plane of the thicker edge of the strip 4 is defined by the plate 31 and the plane of the narrower side of the strip 4 is defined by a shaver or scraper 39 disposed on the opposite side of the strip 4 to the plate 31. The shaver 39 may be in a fixed position. Downstream of the scraper is an idling roller 40 bearing on the narrower side face of the strip and thereby assisting the maintenance of straightness of the strip 4.

Figure 6 is a sectional view through the strip 4 adjacent the plate 31, the rollers 2 and 3 having been omitted for convenience. The plate 31 rests on a deck 40 in which is disposed a recess 41 accommodating, removably, a post 42. This post supports the underside of the strip 4 at a location spaced from the ridge 38. There is a space between the strip 4 and the deck 40. Into this space may fall dust or swarf produced by the shaving of the strip.

In general, such as where the reduction in crosssectional area of a strip is reduced by up to 70% the required taper may be produced by the rolling of, for example, a copper strip of rectangular crosssection in a single pass through the rollers. Normally the change in cross-sectional area would be between 30% and 70% in a single pass, for strips with a section depth between 15 and 45mm.

In the foregoing it is presumed that the strip is straightened (against the tendency to curl imposed by the rollers) by the forcing of the strip against the portions of the guide 31 between and downstream from the rollers and by the application of a controlled pull by means of the draw bench. However, it has been found that a strip having a thin section (such as between 15mm and 25mm) deep or a very shallow angle of taper can be satisfactorily straightened by setting the guide 31 at a slight angle to the longitudinal axis of the strip; the use of the draw bench is then not normally required.

The construction of the guide assembly 5 on the upstream side of the frame 1 is not of direct importance to the present invention, but preferably comprises sets of rollers engaging each side of the strip. Each of the rollers may be movable in a direction transverse the strip and preferably comprises a hub freely mounted for rotation and a metal skirt which fits over the hub.

Claims (10)

1. Apparatus for cold rolling malleable strip into tapered cross-section, comprising a pair of rollers, means for setting the rollers at a relative angle defining the taper of the cross-section, and a static guide which extends downstream from the rollers and provides for defining a datum for the thicker side of the strip.

2. Apparatus according to claim 1 in which the static guide comprises a plate of which a narrow face defines the said datum.

3. Apparatus according to claim 2 in which the plate is scalloped in its broad faces for the accommodation of the rollers.

4. Apparatus according to claim 2 or claim 3 in which the guide includes a member positioned for the support of an underside of the strip, the member extending downstream along part of the said narrow face of the plate.

5. Apparatus according to any foregoing claim in which the static guide supports the strip at a level spaced above a deck.

6. Apparatus according to any foregoing claim in which a scraper is disposed in a position on the opposite side of the strip to that of the said guide.

7. Apparatus according to claim 6 in which a guide roller is disposed to engage the narrower side of the strip at a position downstream from the scraper.

8. Apparatus according to any foregoing claim, further comprising means for drawing the strip between the rollers.

9. A method of cold rolling a strip of malleable metal into tapered cross-section, comprising passing the strip through a pair of rollers which are set at an acute angle defining the taper of the crosssection and supporting the thicker side of the strip after the rollers by means of a static guide.

10. A method according to claim 9 in which the cross-section of the strip is altered from substantially rectangular to a required section by means of a single pass through the pair of rollers.