Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
2000-05-26
2001-12-25
Cuda-Rosenbaum, I (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S888023, C029S558000, C418S201100, C418S195000
Reexamination Certificate
active
06332271
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for making rotors for screw-type machines, in particular rotors having a large flight depth and a small pitch.
2. Description of the Related Art
In the area of machinery, screw-type machines are increasingly replacing the reciprocating-piston or gear machines hitherto used in many areas. The known piston compressor, for example, has been replaced by screw-type compressors in the industry. Similarly, screw pumps have replaced gear-type lubricating oil pumps in industrial plants.
All screw-type machines have a rotor which, in conjunction with one or more secondary rotors and/or the surrounding casing, forms closed delivery chambers into which a medium being conveyed is transported from an inlet side to an outlet side of the machine. Rotors of this type have hitherto been produced on milling or grinding machines by the hobbing method. This production method has been technically and commercially useful for rotors of screw compressors or for screw pumps for lubricating oil which have a large pitch in combination with a small flight depth and are produced in large quantities. In this case, a corresponding machining tool (profile milling cutter or formed wheel) is required for each rotor geometry (diameter, pitch, profile shape). The resulting tool costs and set-up times are acceptable for large scale production.
However, when producing rotors with a large flight depth and a small pitch which are produced individually or in very small quantities for special machines, the above-mentioned method is particularly costly, because of the tool costs and set-up times. In the case of special flank profiles, as described for a feed screw pair, e.g. in DE 42 24 969 C1, technical feasibility is limited to a considerable extent when using the above production method.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an economical production method for rotors of screw-type machines, particularly for rotors with a large flight depth and a small pitch.
This object is achieved according to the invention by producing the profile geometry using a three-dimensional plunge-cut turning method for which a recessing tool for cutting a groove of rectangular cross section and respective special tools for shaping the right-hand and left-hand profile flanks are used and clamped in a holding fixture which is set about an axis of rotation, which intersects at a right angle to the work piece axis of the work piece to be machined, to the mean pitch angle of the rotor flight to be produced, and after which the following machining steps are carried out:
a first machining step, in which an approximately rectangular groove is plunge-cut approximately at the center of the profile with trilateral machining; in subsequent steps, this groove is cut radially deeper with the same recessing tool with trilateral machining until a groove depth of several millimeters has been reached; the profile flanks are then shaped by bilateral machining with the special tools mentioned, for which the plunge-cut groove serves as a tool runout; just before this profiling reaches the groove depth previously produced, this work step is ended and, instead, the groove depth is increased with the aid of the recessing tool, the previously shaped profile width now serving as a tool runout for the recessing tool; and the above-mentioned method steps are repeated until the entire profile geometry has been produced with its profile base.
The machining tools for the rectangular groove and the right-hand and left-hand profile flanks are thus preset to the mean pitch angle of the rotor flight before the beginning of production, being either rotated appropriately in their holding fixture or set appropriately together with the holding fixture.
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patent: 5377407 (1995-01-01), Takahashi et al.
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patent: 6098266 (2000-08-01), Kirsten
patent: 6122824 (2000-09-01), Jensen
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patent: 42 24 969 (1992-07-01), None
Koenigsberger et al., Rotorfertigung fuer Schraubenkompressoren, Werkstatt unfd Betrieb 114 (1981) pp. 463-465.
Kurzberichte, Wirbelmaschine fuer Schraubenverdichter-Rotoren, wt-Z. ind Fertig. (1973) Nr. 10 (1973) pp. 647-648.
Cuda-Rosenbaum I
Foley & Lardner
Joh. Heinr. Bornemann GmbH
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