The present invention relates to the manufacture of pipe. More particularly this invention concerns pipe made from a tubular workpiece.
It is known to forge a long tube, e.g. a piece of pipe, from a prepunched or tubular workpiece. To this end the tubular workpiece is gripped by a handler and brought into the working space of a forging machine. Before the tubular workpiece is forged in the forging machine a mandrel on a rod is inserted axially through a guide passage in the handler and into a bore of the tubular workpiece. Tools of the forging machine plastically deform the metal of the workpiece so it internally conforms to the outside shape of the mandrel, such deformation normally thinning the walls and lengthening the workpiece.
The forging machine has several tools or forging jaws acting radially on the tubular workpiece. The tubular workpiece fed or loaded on the charging side upstream of the forging machine, for example, by pivoting is gripped and held by the workpiece handler, e.g. by grippers, as is known for example from U.S. Pat. No. 5,218,855. In the tubular workpiece thus held by the workpiece handler for forge handling, the rod with the mandrel on its end, which can be acted on axially by a control drive, is moved through a hollow passage of the workpiece handler.
The centered insertion of the mandrel into the tubular workpiece hereby is fairly difficult, especially in view of the great length of the rod, which promotes deflection.
It is known from DE 200 07 682 to guide the rod in a holding fixture provided for the axial support and rotational engagement of the workpiece, which holding fixture is supported in a clamping head housing in a rotationally and axially displaceable manner. The holding fixture has for this purpose a guide sleeve in which a bushing surrounding a guide section of the rod is rotatably fixed. The disadvantage of this solution is that the rod guidance is very complex, which results in corresponding costs.
It is therefore an object of the present invention to provide an improved pipe-making method and apparatus.
Another object is the provision of such an improved pipe-making method and apparatus that overcomes the above-given disadvantages, in particular that render possible in a simple manner a central insertion of the mandrel into the tubular workpiece and thereby rule out deflection of the rod as far as possible.
According to the invention the tubular workpiece is held by a handler having a passage alignable with the bore and of a predetermined inside passage diameter. A rod carrying a mandrel and of an outside rod diameter is provided with a guide having an outside guide diameter slightly smaller than the inside passage diameter but greater than the outside rod diameter The passage is aligned by the handler with the workpiece bore and the mandrel is inserted through the handler passage into the workpiece bore while sliding the guide along the passage and centering the rod in the passage with the guide out of contact with an inner surface of the passage. The workpiece is externally engage around the mandrel with forging tools and thereby forged around the mandrel.
The centering guide is thereby preferably held in the forging machine axially outside the tubular workpiece and inside the passage during the entire forging process.
The bore of the tubular workpiece and/or the mandrel are preferably provided with a lubricant or release agent before the insertion of the mandrel into the bore of the tubular workpiece.
The bore of the tubular workpiece and the mandrel are designed with respect to their diameter such that no contact occurs between the mandrel and the bore of the tubular workpiece during the axial insertion of the mandrel into the bore of the tubular workpiece and before the forging process.
The apparatus for producing pipe from a prepunched tubular workpiece comprises a workpiece handler with a passage for gripping and axially displacing the tubular workpiece, a forging machine and a rod with a mandrel arranged thereon for the axial movement through the guide passage in the workpiece handler and for axial insertion into the bore of the tubular workpiece. The apparatus is characterized according to the invention in that the rod has a centering guide whose outside diameter is slightly smaller than or equal to the inside diameter of the passage of the workpiece handler and the outside diameter of the rod is smaller than the outside diameter of the centering guide.
According to a preferred embodiment, the centering guide has at least two parts, concentrical to one another. In particular an inner part has a part-spherical outer surface embodied that engages a complementary surface of outer part. The centering guide can be provided on its outer surface with at least one chamfer.
The centering guide can be axially fixed on the rod on both sides by clamps.
The diameter of the bore of the tubular workpiece is preferably greater before the forge processing thereof than the outside diameter of the mandrel.
In the proposed solution, the rod with the mandrel is centered in the passage of the workpiece handler in an advantageous manner and thus directly at the site of the action and centrally supported therein during the axial control movements of the handler and/or of the rod actuator guided over the entire length of the passage.
To this end, the rod is provided with a centering guide or centering ring, the outside diameter of which corresponds approximately to the inside diameter of the passage of the workpiece handler.
The proposed approach and apparatus are used advantageously in particular with pipe forging. A functional centering of the combination of mandrel and rod occurs inside the workpiece handler.
Deflection of the relatively long rod can be efficiently prevented or in any case substantially minimized by the use of the centering guide. The mandrel can be inserted centrally into the tubular workpiece.
The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:
As seen in
For maneuvering the rod 4 it is supported near the workpiece handler 2 on an upstream support 15′ and on other supports 15 spaced downstream therefrom in the first step of
Then as shown in
According to
Subsequently, as shown in
According to
The forging itself is carried out as shown in
The important factor is that the rod 4 has at least one centering guide 8, here only one. Details in this regard are shown in
An outside diameter DZ of the centering guide 8 is slightly smaller than an inside diameter DI of the passage 6 of the workpiece handler 2; at most, it is of the same size. However, an outside diameter DA of the rod 4 is smaller than the outside diameter DZ of the centering guide 8.
As a result, the rod 4 can be guided through the passage 6 of the workpiece handler 2 such that there is contact between the outer surface of the centering guide 8 and the inner surface passage 6 of the workpiece handler 2, but there is no contact between the rod 4 and the passage 6 of the workpiece handler 2.
The structure of the supporting centering guide 8 is very advantageous as shown by
The inner part 8′ has a part-spherically convex outer surface 9 as shown in the diametral section of
During insertion of the mandrel 5 into the bore 7 of the tubular workpiece 1, it is possible due to the precise centering of the mandrel 5 and the mandrel rod 4 to avoid the mandrel 5 ever touching the inner wall of the bore 7. The wall of the bore 7 as a rule is coated or provided with a lubricant or release agent. Accordingly, during insertion of the mandrel 5 into the bore 7 an air gap remains between the mandrel and the bore 7, as indicated in
Furthermore as indicated in
Deflection of the rod 4 inside the tubular workpiece 1 is therefore considerably reduced by the centering guide 8 on the rod 4
Number | Date | Country | Kind |
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10 2009 008 396 | Feb 2009 | DE | national |
10 2009 052 482 | Nov 2009 | DE | national |
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