Metal deforming – By use of tool acting during relative rotation between tool... – During rotation of work
Reexamination Certificate
1999-11-26
2001-03-27
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of tool acting during relative rotation between tool...
During rotation of work
C072S085000
Reexamination Certificate
active
06205832
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims priority from German Patent Application Serial No. 198 54 481.2, filed Nov. 25, 1998, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a flow-forming method in which an axially symmetrical workpiece is fixed at a free end of a spinning mandrel having an external profile; the spinning mandrel together with the workpiece are rotated and at least one spinning roll is infed, said workpiece being shaped to the external profile of the spinning mandrel.
The invention also relates to a flow-forming apparatus with a spinning mandrel having an external profile and on which can be fixed a workpiece, a drive by which the spinning mandrel and the workpiece can be rotated together and at least one spinning roll for shaping the workpiece to the external profile of the spinning mandrel.
2. Description of Related Art
Methods and apparatuses of the same species are adequately known. For example, a cup-shaped starting workpiece is mounted on a spinning mandrel with a substantially cylindrical outer contour and the axially extending edge of the workpiece is shaped initially by radial and/or axial infeeding of a spinning roll to the spinning mandrel. External teeth can be provided on the spinning mandrel so that these external teeth are pressed into the cup-shaped workpiece. In the known methods and apparatuses, it is problematical that, as a result of the action of the spinning roller, considerable forces are exerted on the external teeth of the spinning mandrel so that, during the pressing in of the teeth, high bending stresses and repeated stress reversals occur on the individual tool teeth. After a relatively short time, these stresses can lead to tooth breakage and consequently to the destruction of the spinning mandrel.
In the flow-forming, cup-shaped, internally toothed workpiece, the problem exists that, at the free edge of the workpiece, the teeth are frequently not completely shaped. Thus, workpieces are conventionally worked with a certain axial oversize which must subsequently be dressed by machining.
Rechucking and dressing in a further working machine are disadvantageous. It is particularly problematical that, on the dressed edge of the internal teeth, a burr is left behind, which can hardly be removed mechanically, so that frequent manual deburring is required.
SUMMARY OF THE INVENTION
The object of the invention is to provide a method and an apparatus permitting a geometrically accurate manufacture of workpieces with an internal profile.
The invention is based on a prior art method in that, spaced from the free end of the spinning mandrel, there is mounted thereon a spacing ring or spacer made from a deformable material. On forming a marginal area of a first workpiece, the deformable material is shaped on the spacer. The spacer, during the shaping of the marginal area of the first workpiece, is plastically deformed and work hardened while the deformed and hardened spacer is left for shaping further workpieces on the spinning mandrel.
Thus, during the workpiece forming process, the spacer adapts to the complex play of forces. An inexpensively manufacturable spacer is adapted in an almost optimum manner to the external profile of the spinning mandrel. As a result of the interplay of materials during shaping, the spacer and workpiece firmly engage with one another, so that there is a uniform, rounded edge contour on the face of the workpiece. This rounded edge contour is particularly advantageous with regard to tribological characteristics.
The deformation of the spacer takes place plastically. Following the forming process, the spacer is work-hardened and dimensionally stable. The spacer can be made from the same material as the workpiece. During forming, a hardened and a stable final shape of the spacer is obtained.
The method according to the invention is particularly suitable for shaping the workpiece in an external profile provided on the lateral face of the spinning mandrel. It can be a tooth system or a keyway profile, such as is required for a clutch disk carrier. In one working step, simultaneously the forming area of the workpiece is brought axially and radially into the desired shape and a hardened surface structure is provided in the inner forming area.
Preferably, the spacer is mounted on the spinning mandrel in such a way that it partly covers the teeth with an overlap area which, during the shaping of the workpiece and the deformation of the spacer, is at least partly shaped into the tooth system. Thus, the spacer is given a reliable hold on the spinning mandrel. The tooth system is additionally supported, which significantly increases the tool life.
The method is particularly advantageous in that, as a result of the shaping of the workpiece at the lateral face, there is an axial material flow which is partly decelerated by the face of the spacer. Radially outer material of the workpiece flows further axially and at least partly overflows the spacer so that, through the radial force component applied by the spinning roll or rollers, the spacer is radially deformed. Thus, the outer edge of the finished workpiece is clearly defined by the stop on the face of the spacer, while excess material flows on axially and consequently comes to rest on the outside of the spacer.
Preferably, the spacer is frontally formed with concave depressions and can extend axially by 0.2 to 0.5 mm. As a result, the workpiece material is shaped in such a way towards the spacer that the faces of the resulting internal teeth form a mirror image of the concave depressions of the spacer with a convex or corrugated structure.
The method is further developed in a particularly advantageous manner in that the wall thickness of a material overflow caused by shaping is rolled virtually to zero by further axial advance of the spinning roll. Thus, in an advantageous manner, any material excess present can easily be removed by cutting it off. However, the edges on the tooth system are not affected by such a deburring.
The method according to the invention is particularly advantageous in that, after the removal of the finished workpiece, the method is repeated with the same deformed and dimensionally stable spacer for the purpose of forming a further workpiece. This repetition leads to identically formed or shaped workpieces and working always takes place to an internal shape, which has the ideal contour provided through the first forming process.
It can also be advantageous if simultaneously several spinning rolls act at different points on the workpiece. This action reduces the local loading of the spinning mandrel and consequently also on the tooth systems. The spinning mandrels are also protected due to the lower forces which arise.
The invention builds up on a prior art apparatus in that a deformable spacer is provided, that the spacer is replaceably fixable to the spinning mandrel and that, during the forming of a first workpiece, the spacer is shapable and fixable to the external profile of the spinning mandrel. An overlap area overlaps at least partly with the workpiece area during workpiece shaping. The advantages of the method can be implemented with this apparatus according to the invention. The spacer can be simply and inexpensively manufactured. It can be replaced easily when changing the axial workpiece length.
It is particularly advantageous to place a pressing disk for fixing the workpiece so as to face the front of the spinning mandrel. As a result, the workpiece can be received in an advantageous manner by the spinning mandrel and it can be given an adequate hold so as to withstand the forces which occur.
The spinning mandrel preferably has a shaping area with a first diameter and a rear area with a second diameter, the first diameter being larger than the second diameter. Thus, the spinning mandrel can be fixed in a driven receptacle, while the shaping area diameter is adapted to the workpiece to be produced.
The shaping area of the spinning mandrel has a t
Larson Lowell A.
Leico GmbH & Co. Werkzeugmaschinenbau
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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