This invention relates to improvements in press tools for producing metal components.

In known press tools a blank is placed on top of a die supported on a bolster and, on descent of a ram, a punch carried by the ram bends the blank to a desired shape to form the component and which is determined by the shape of the die into which the punch enters. During the initial movement of the punch into the die a cupping step is carried out to form a relatively flat disc or sheet into a cup and, during a subsequent step or movement of the punch, which may comprise a continuous operation with the first step, the component may be drawn down to increase its depth or length accompanied by a corresponding reduction in the wall thickness of the component.

When producing a metal component by cold drawing down, depending upon the depth of the final component, it is often necessary to perform the drawing operation in several steps or stages. This is necessary in order to avoid possible cracking or other unacceptable and undesirable deformation of the material which may occur due to excessive stresses in the material which are set up if the production of such a component in a single press operation is attempted. However, drawing down in several steps or stages has the disadvantage that, in addition to being time consuming, the walls may be variable in thickness depending on a previous, or the previous draw point which, in the final product, means that the wall is of stepped configuration and of correspondingly reduced strength. In addition it is difficult to maintain the accuracy of shape and configuration between components produced by such a

SUBSTITUTE SHEET

process due to tolerance variations in the gauge of material itself and between the punches and the dies. This, in turn, affects the accuracy of further manufacturing or finishing steps.

According to our invention in a press tool for producing metal components comprising a die and a punch which are relatively movable towards and away from each other, the die is provided with rotatable rollers with which a component co-operates during a drawing operation in which the punch enters a cavity in the die cavity.

The blank is therefore drawn down between the punch and the rollers. Since the rollers rotate freely with the frictional engagement of the component, the press forces are relatively reduced and a conventional press deformation step is replaced, at least in part, by a rolling operation. This achieves, in the finished component, a more even wall thickness and an improved surface finish on the external faces which co-operates with the rollers.

Since the blank can be drawn down in a single operation, stepping in the final product is avoided with a corresponding increase in the strength of the component.

In addition to saving time, the production of a component by a single operation in a single tool reduces the cost of tooling and the cost of the component itself.

The rollers may be provided on opposite sides of the die cavity for rotation about spaced axes which lie in a common plane. In such a construction the rollers

are journalled for free rotation at opposite ends in bearings in opposite end walls of the die.

The rollers may be of any chosen shape and configuration consistent with the final required shape of the component. For example, when the component is generally of channel outline and the base from which side flanges are upstanding is of reduced width at opposite ends, the rollers are symmetrically arranged and have portions of reduced diameter intermediate opposite end portions.

One embodiment of our invention is illustrated in the accompanying drawings in which:-

Figure 1 is a internal plan view of a press tool;

Figure 2 is a section on line 2-2 of Figure 1;

Figure 3 is a section on line 3-3 of Figure 1; and

Figure 4 is an inverted plan showing the profile of the roller.

The press tool illustrated in the accompanying drawings comprise a housing 1 for a die 2 and a relatively movable punch 3 which is movable in an upward direction into a cavity 5 in the die towards a stop face 4 upon operation of a pressure medium, for example pressure rams 6. Upward movement of the rams 6 is accompanied by a corresponding movement of a platen 15 comprising an end wall of a piston 16 which is operated by the pressure medium in conjunction with the rams 6.

The punch 3 comprises a pressure pad 7 having an external profile corresponding to the internal profile of a metal component 8 to be produced.

A pair of rollers 9, 10 are mounted in the die cavity 5. The rollers 9, 10 are each journalled for rotation at opposite ends in bearings 11 housed in the end walls of the die cavity 5. The rollers 9, 10 are disposed in a spaced parallel relationship and their axes lie in a common plane parallel to and spaced from the stop face 4. The two rollers 9, 10 are each of a profile complementary to that of the side faces of the pressure pad 7, for example of dumb- bell outline as shown, having symmetrically arranged intermediate portions 12 of reduced diameter smaller than the diameters of opposite end portions 13.

Coining portions 20 of the wall at the upper end of the die cavity 5 adjacent to the rollers 9, 10 are of similar profile to the rollers 9, 10.

Component strippers 21 are located at the opposite end of the die cavity 5 through which the punch 3 works during the deforming operation.

In operation the pressure pad 7 of the punch 3 and the platen 15 are retracted to a position through the rollers 9, 10 in which they are disposed adjacent to the end wall of the die cavity 5 which is remote from the coining portions 20. In this position the pressure pad 7 separates from the platen 15 by a distance at least equal to the thickness of the material of a developed blank for forming the component 8.

The blank is placed on the pad 7 by a feed mechanism, and is located in position on the pad 7 by

pins 14. The pressure pad 7 is then raised to clamp the blank between the pressure pad 7 and the platen 15. The pad 7 and the platen 15 are then raised together, under a pressure substantially of 8 Tonnes, with the blank fed between the rollers 9 and 10 which rotate freely due to the frictional engagement of the blank with them.

Thus the side edge portions of the blank are deformed downwardly and drawn down by cold drawing to form four side flange portions 24 by the rolling deformation of the material as a result of relative movement between the punch 3 and the die 2, and the final coining of the edges of the component by engagement with the coining portions 20.

This movement continues until the piston 16 engages with the stop face 4. The pressure applied to the component 8 is maintained for a period of time necessary to size up the component. Due to the magnitude of the applied pressure the component is accurately sized to the configuration of the punch 3.

The punch 3 and the platen 15 are then retracted together back through the rollers 9, 10 until the component co-operates with the strippers 21. Thereafter the component is ejected from the press and is replaced by another blank. The sequence of operations defined above is then repeated.

Forming the components in a single operation in a single press improves the quality and strength of the components and conserves time and energy.

In a modification the location of the die 2 and the punch 3 are reversed so that, during the forming

operation, the punch 3 is lowered through the rollers 9, 10.