Forming machine, method for forming a product and exhaust system or pulley comprising such a product

Abstract

 The invention relates to a forming machine (1) comprising a rotatably drivable gripping device (2) for gripping a workpiece, such as a plate of stock material, for example, which gripping device comprises a first forming tool (3) and a press-on tool (4) for pressing the workpiece in the direction of said first forming tool. The forming machine furthermore comprises a second forming tool (18), which is mounted at least substantially coaxially round the press-on tool, which second forming tool can be moved along the press-on tool. With the forming machine according to the invention the workpiece can be worked in two opposite directions without there being a need to remove the workpiece.

Description

[0001] The invention relates to a forming machine comprising a rotatably drivable gripping device for gripping a workpiece, such as a plate of stock material, which gripping device comprises a first forming tool and a press-on tool for pressing the workpiece in the direction of said first forming tool.

[0002] A forming machine of this kind is known for example from EP-A-0 125 720. With such a forming machine the workpiece is formed by gripping it between the forming tool and a press-on tool or loose head, and subsequently moving a forming roller in a path that corresponds to the shape of the forming tool. Thus a cylindrical, oval-cylindrical or conical body having a flat bottom is for example obtained. For more complex shapes, with the wall being deformed in two or more opposite directions, as is for example the case with parts for exhaust systems or pulleys intended for use in the automobile industry, but also with ashtrays, for example, it is necessary to remove the workpiece and grip it in a second forming machine. Subsequently, a deformation in a second, substantially opposite direction is carried out in said second forming machine.

[0003] With each subsequent deforming step in another direction the workpiece needs to be removed and be placed in a next forming machine. These operations take a great deal of time and, in addition, they will frequently result in inaccuracies when a workpiece must be gripped repeatedly, which may result in products exhibiting dimensional variations that fall outside the required or desired range of tolerances.

[0004] The object of the invention is to provide a forming machine of the kind referred to in the introduction, wherein the above drawbacks are overcome or at least substantially alleviated.

[0005] In order to accomplish that object the forming machine according to the invention is characterized by a second forming tool, which is mounted at least substantially coaxially round said loose head, which second forming tool can be moved along the press-on tool or the loose head.

[0006] Once a workpiece is fixed by gripping, this second forming tool is located on the side of said workpiece remote from the first forming tool. By pressing the second forming tool against the workpiece after a first deformation of the workpiece on the first forming tool, and changing the axial position of said second forming tool with respect to the loose head, the workpiece can be deformed by means of a forming roller in the direction of the second forming tool. The workpiece need not be removed thereby, as a result of which the time-consuming removing and renewed gripping of the workpiece is no longer required and, in addition, shifting of the workpiece cannot take place.

[0007] If the shape of the workpiece makes it necessary to reverse the direction of deformation i times (i = 1, 2, 3, .....), it is possible to provide i additional forming tools. Thus it is possible to mount a third forming tool co-axially round the first forming tool, which third forming tool can be moved along the first forming tool.

[0008] An effective way of ensuring that the additional forming tools cannot rotate with respect to the forming tool or the loose head on which they are mounted, whereas translating movement is possible, is for example the use of key-ways. Key-ways are easy to make, they allow translating movement and they ensure an effective transmission of forces and torques between the parts that are fitted together.

[0009] In principle, the forming machine according to the invention can be fitted with a single, preferably symmetrical forming roller, which can be moved to the other side of the workpiece with each subsequent deforming step.

[0010] The invention furthermore relates to a method for forming a product, wherein a workpiece, for example a plate of stock material, is gripped between a first forming tool and a press-on tool or loose head, and is deformed on the first rotary forming tool by moving a forming roller in a path that corresponds to the shape of the first forming tool. The method is characterized in that subsequently a second forming tool is placed in abutment with the workpiece, on the side remote from the first forming tool, and that the workpiece is deformed on the second rotary forming tool by moving a forming roller in a path that corresponds to the shape of the second forming tool.

[0011] The invention will be explained in more detail hereafter with reference to the drawings, which show exemplary embodiments of the forming machine according to the invention.

[0012] Figure 1 is a schematic top plan view of a forming machine according to the invention.

[0013] Figure 2 is a partial schematic sectional view of the gripping device of the forming machine according to Figure 1.

[0014] Figures 3A - 3F schematically show six steps of a method according to the invention.

[0015] Figure 1 schematically shows a top plan view of a forming machine 1 according to the invention, which comprises a rotatably drivable gripping device 2. Gripping device 2 comprises a first forming tool or chuck 3 and a press-on tool or loose head 4, which are mounted coaxially in such a manner as to be capable of rotating movement. Chuck 3 can be driven by means of an electric motor (not shown).

[0016] A workpiece, for example a disc-shaped metal plate as shown in figures 2 - 3F, can be gripped between the first forming tool or chuck 3 and the loose head 4 in a manner that is known per se. Such a metal plate may for example have a thickness ranging from 1 - 12 mm preferably from 1 - 3 mm, and a diameter of 200 - 700 mm, and it can be formed into a desired product by means of a forming roller 5, which is rotatably mounted in a holder 6. Holder 6 is supported in a manner which is known per se by a movable Y-slide or upper slide 7, which is mounted on a movable X-slide or lower slide 8. Lower slide 8 is translatably mounted on machine bed 9 of the forming machine 1. Slides 7, 8 and their respective driving means are accommodated in a housing. Since these parts are not essential for the present invention, reference is made to the applicant's Dutch patent application no. 1000851 and to European patent application no. 0 125 720 for a more detailed explanation.

[0017] The forming machine furthermore comprises a control part 10, which includes a control unit, an input device, for example in the form of a keyboard, a display screen and a memory. The shape of chuck 3 is stored in the memory of the control part with a view to forming the metal plate on chuck 3 in the production stage. The path to be followed by forming roller 5 is then determined in the usual manner, taking into account the thickness of the metal plate, for example as disclosed in applicant's Dutch patent application no. 1001675.

[0018] Figure 2 shows the gripping device 2 of the forming machine 1 in more detail. First chuck 3 is circular in section, with the diameter varying in axial direction. The end 11 of chuck 3 has the smallest diameter, which gradually increases in axial direction, so that a frustoconical shape is obtained. From there the diameter of first chuck 3 then increases in steps and subsequently it remains constant along the remaining length of chuck 3.

[0019] Positioned opposite first chuck 3 is the loose head 4, which comprises a cylindrical pre-bearing shaft 12 and a conical press-on disc 13. The diameter at the end of press-on disc 13 is identical to the diameter at the end 11 of first chuck 3. Pre-bearing shaft 12 is supported in a first group of bearings 14 and a second group of bearings 15, with said second group of bearings 15 being mounted round a hollow cylindrical part 16, which hollow cylindrical part 16 is mounted on pre-bearing shaft 12 by means of key-ways (not shown). Hollow cylindrical part 16 furthermore comprises a flange 17, to which a second chuck 18 is fixed. When second chuck 18 is connected to the pre-bearing shaft 12 in this manner, there is no need to provide additional bearings for said second chuck.

[0020] After a workpiece, in this case a disc-shaped metal plate 19, has been gripped between first chuck 3 and loose head 4 and has been worked in a first processing step, so that it conforms to the shape of end 11 of first chuck 3, the second chuck 18 is placed in abutment with the deformed disc-shaped metal plate 19. To this end the shape of second chuck 18 is at least partially complementary to the shape of first chuck 3, so that second chuck 18 will be capable of accommodating the end 11 of first chuck 3 and the deformed disc-shaped metal plate 19 and of contributing to the gripping force that is exerted on the metal plate 19.

[0021] Mounted round first chuck 3 is a third chuck 20, also in this case by means of key-ways, for example. The shape of third chuck 20 is partially complementary to that of second chuck 18, so that said third chuck 20 will be capable of accommodating part of second chuck 18 and the deformed disc-shaped metal plate 19 and of clamping it against second chuck 18.

[0022] Figures 3A - 3F schematically show six steps of a method for forming a product, in this case again a disc-shaped metal plate 21. The gripping device as shown corresponds largely to the gripping device that is shown in figure 2.

[0023] Before the deforming operation is started, the disc-shaped metal plate 21 is clamped between the conical end 22 of first chuck 23 and the end 24 of a loose head 25. The present forming machine comprises a holder 26, on which a first forming roller 27 and a second forming roller 28 are rotatably mounted. Holder 26 is symmetrical in shape, and the forming rollers 27, 28 are mounted in mirror symmetry with respect to the plane of symmetry of holder 26. It stands to reason that it is also possible to use one forming roller or for example a tool exchanger fitted with 2 to 5 forming rollers, for example. Once the workpiece is gripped, the first chuck 23 is driven, generally at a number of revolutions ranging between 500 (for plates having a large diameter) and 2400 (for plates having a small diameter), and the loose head 25 is driven by workpiece 21.

[0024] The first forming roller 27 is placed in abutment with the workpiece at the location of the point of contact of the end 24 of loose head 25, and then it is moved in a path that corresponds to the shape of first chuck 23. After workpiece 21 has taken on the shape of the end 22 of chuck 23, first forming roller 27 is removed from workpiece 21 and holder 26 is moved to the other side or rear side of workpiece 21.

[0025] Then a second chuck 29 is placed in abutment with workpiece 21, and second forming roller 28 is moved into contact with the other side of workpiece 21. Then the forming roller 28 is moved in a path that corresponds to the shape of second chuck 29, and after the second deforming step is complete the second forming roller 28 is moved away from workpiece 21 and holder 26 is moved to the other side of workpiece 21 again.

[0026] A third chuck 30 is moved into contact with the rear side of workpiece 21, whilst the first forming roller 27 is moved into contact with the front side of workpiece 21. Then the first forming roller 27 is moved in a path that corresponds to the shape of third chuck 30. Following this, the workpiece 21 can be removed from the gripping device by moving the second and the third chuck 29, 30 and the loose head 25 away from the workpiece 21.

[0027] The forming machine and the method according to the present invention make it possible to form a workpiece in two substantially opposite directions without there being a need to remove the workpiece. This makes it possible to reduce the production times and avoid the inaccuracies that may occur when the renewed gripping of the workpiece is necessary.

[0028] It is noted that the chucks do not necessarily have to be of circular section. Thus it is possible, for example, for the first chuck to have a circular section, whilst the second chuck has an oval outer circumference that corresponds to the outer circumference of the second chuck, whilst the outer circumference of the third chuck is circular again.

[0029] The forming machine and the method according to the invention are for example very suitable for manufacturing shells for use in exhaust systems of e.g. trucks.

[0030] The invention is not restricted to the above-described embodiments, which can be varied in several ways within the framework of the claims. Thus the gripping device may also be positioned vertically (rotatable about a vertical axis). Such an arrangement facilitates horizontal transport and positioning upon subsequent processing steps of the workpieces, which has significant advantages, in particular in case of mass production.

Claims

1. A forming machine comprising a rotatably drivable gripping device for gripping a workpiece, such as a plate of stock material, which gripping device comprises a first forming tool and a press-on tool for pressing the workpiece in the direction of said first forming tool, characterized by a second forming tool, which is mounted at least substantially coaxially round the press-on tool, which second forming tool can be moved along the press-on tool.

2. A forming machine according to claim 1, wherein a third forming tool is mounted coaxially round the first forming tool, and wherein said third forming tool can be moved along said first forming tool.

3. A forming machine according to claim 1 or 2, wherein said second forming tool and/or said press-on tool and/or said third forming tool is (are) movably mounted on said first forming tool by means of key-ways.

4. A forming machine according to any one of the claims 1 - 3, wherein the shape of said second and/or said third forming tool is at least partially complementary to the shape of the first and/or the second forming tool, respectively, complemented with the local thickness of the workpiece.

5. A forming machine according to any one of the preceding claims, which machine comprises two or more forming rollers.

6. A forming machine according to claim 5, wherein said forming rollers are mounted on the same holder.

7. A method for forming a product, wherein a workpiece, for example a plate of stock material, is gripped between a first forming tool and a press-on tool or loose head, and is deformed on the first rotary forming tool by moving a forming roller in a path that corresponds to the shape of the first forming tool, characterized in that subsequently a second forming tool is placed in abutment with the workpiece, on the side remote from the first forming tool, and that the workpiece is deformed on the second rotary forming tool by moving a forming roller in a path that corresponds to the shape of the second forming tool.

8. A method according to claim 7, wherein a third forming tool is placed in abutment with the workpiece, on the side remote from the first forming tool, after deformation of the workpiece on the second forming tool, and wherein the workpiece is deformed on the third rotary forming tool by moving a forming roller in a path that corresponds wo the shape of the second forming tool.

9. An exhaust system or a pulley comprising a hollow product having a specific wall thickness, which has been obtained by means of the method according to claim 7 or 8.

Drawing