Metal deforming – By use of tool acting during relative rotation between tool... – During rotation of work
Reexamination Certificate
1999-05-07
2001-05-08
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of tool acting during relative rotation between tool...
During rotation of work
C072S075000, C072S097000
Reexamination Certificate
active
06227024
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a flow-forming method, in which a preform or blank is fixed to a spinning chuck and is formed or worked by means of at least one rolling member, the blank rotating about a rotation axis relative to the rolling member. The invention also relates to a flow-forming device having a forming device with at least one rolling member, a spinning chuck on which is held a blank and which is axially displaceable relative to the forming device and a drive for rotating the blank relative to the forming device.
2. Discussion of the Background Art
DE 42 18 092 Cl and DE 196 36 567 A1 describe a method for the manufacture of a circular cylindrical gear part, on a part of whose axial length are formed internal teeth by flow-forming. With this method, a part can be manufactured in a very reasonable manner, which could otherwise only be manufactured at high cost by a cutting procedure. The advantage of manufacture by flow-forming is a virtually final contour-near production, accompanied by a high dimensional stability and a limited peak-to-valley height of the parts produced. Simultaneously material hardening is brought about in the region near to the surface, which has a favorable affect on the wear performance and fatigue strength. During forming, the blank is spun in the tooth profile of a tool by means of one or more spinning rollers, the teeth being completely filled. However, the high loading of the tooth profile of the tool is disadvantageous in this manufacturing procedure. When rolling in the internal teeth, as a result of the penetration of material into the tool tooth profile, bending and impact stress occurs to the teeth. The repeatedly occurring alternating loads lead to tool material fatigue. Ultimately cracks form and the tool fails after a short time. These processes are described in detail in DE 197 13 440 A1.
Tools are also known for planishing and workhardening which are based on hydrostatically mounted spherical tools. With the aid of such tools, a plasticizing of metallic surfaces is brought about by balls or rollers, so that marginal areas can be smoothed or workhardened. As a result of the different embodiments of such tools, it is possible to machine variably designable surfaces (e.g. straight or spherical plane surfaces or bores). The forming of larger material volumes and consequently the shaping of new geometries is not possible with such tools because material plasticizing is impossible due to the manufacturing method used. The transmittable forces are too small for this purpose. Each individual forming or working roll is separately mounted. This construction is unsuitable for the shaping and working of larger material volumes.
Methods are also known in which a blank is flow-formed to its external diameter using one or more rollers, the material penetrating the profile of the tool chuck. Another method proposes the axial fixing of the blank and reducing the diameter thereof accompanied by a radial infeed. As a result of the axial fixing the material flows radially as a result of the pressure of the rollers, so that it is pressed into the recesses of the tool chuck.
In all the aforementioned methods, use is made of individually mounted or seated rollers, which roll with their external-diameter on the blank. As a result of the geometrical and strength-caused dimensions of the rollers with their bearings, as a function of the circumference of the blank, only a limited number of rollers can be arranged in a minimum spacing. Due to the geometrically caused spacing between the rollers, it is impossible to completely compensate the bulging of the circumference of the blank due to the high tangential force in this area and the associated material displacement. Thus, alternating loads occur in the vicinity of tool chuck recesses.
Particularly with working teeth with small modules, this alternating loading can lead to material fatigue and therefore to a short lifespan of the tool.
SUMMARY OF THE INVENTION
Therefore the object of the invention is to provide a flow-forming method and device, in which flow-forming is possible in such a way as to protect both the workpiece and the tool.
According to the invention, this object is achieved in that in the aforementioned method, the blank is formed by a plurality of rolling members, which are arranged in a ring-like manner around the rotation axis and are in each case mounted in rotary manner in a cage. The object is also achieved by a flow-forming device having the features for performing this method.
As a result of the mounting of the numerous rolling bodies in a cage, it is ensured that the blank is supported at its circumference during its rotation by the geometrically maximum number of rollers and is simultaneously formed or worked. The forming rollers encircle the blank in planet-like manner on contacting and forming the same. The blank is an axially symmetrical workpiece, which is solid or a premachined hollow body, such as a pipe length or a cup-shaped part.
In known flow-forming procedures as a result of the separate mounting and control of the spindles due to an axial displacement of the rollers, the shaping process is always started by one roller, so that necessarily there is an undesired deflection of the tool until further axially displaced rollers engage. Therefore, due to this alternate deflection of the forming tool, a uniform loading and autocentring is scarcely possible. In the method according to the invention, the force is symmetrically and uniformly transmitted to all the rollers by means of an outer race of a bearing. Thus, all the rollers act simultaneously in the forming process and thereby independently centre and uniformly load the inner tool.
Appropriately, the blank is moved in a relative axial movement through the ring-like rolling member arrangement. In the case of a hollow blank, the rolling members press it onto the spinning chuck. There can also only be a diameter reduction with a solid blank. The rolling members can be located in a common radial plane. When using a cup-shaped workpiece having a cylindrical side wall and a bottom wall, for a precise forming of the cylindrical wall moving the rolling member from the open end towards the bottom of the workpiece.
If, in preferred manner, the blank is formed by conical rolling rolls which roll in a conical outer race in an arrangement inclined to the blank rotation axis, it is possible to obtain an improved centring on introducing the blank into the rolling member arrangement and also a favorable material flow. As a result of an axial displacement and positioning of the rolling bodies with the cage, a positioning and setting of the rolling bodies is possible.
If the blank is formed by rolling members axially displaced with respect to one another in a single shaping process, a greater diameter range can be covered if the following rolling members in each case roll on a smaller internal diameter. Such an arrangement leads to an improved forming force distribution and action on the blank.
In an appropriate method variant, the blank is formed by rolling members which are arranged in a forming device in two parallel planes perpendicular to the rotation axis. This leads to a simplified construction of a cage seating the rolling members.
To be able to perform different forming or working operations on blanks, rolling members with different shapes and sizes can be used in a forming device, such as in a common cage or in different, successively arranged cages. For example, this makes it possible to form in a single setting bodies having different internal profiles in different diameter ranges.
It is also possible by using spherical rolling members to carry out a first forming of a blank, e.g. a circular blank in a first machining plane or area and by means of conical rolling members, in a following, second machining plane or area, to carry out a second forming of the blank. Thus, extensive blank machining can take place in a single setting.
In one embodiment, the radial positioning of the
Larson Lowell A.
Leico GmbH & Co Werkzeugmaschinenbau
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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