Metal working – Method of mechanical manufacture – Prime mover or fluid pump making
Reexamination Certificate
1999-09-28
2001-04-24
Cuda, Irene (Department: 3726)
Metal working
Method of mechanical manufacture
Prime mover or fluid pump making
C029S888061, C029S527200
Reexamination Certificate
active
06219914
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a process for producing a cylinder with at least one outward bulge extending along its length and with a base made of steel for a piston-cylinder unit.
2. Discussion of the Prior Art
In modern mines, especially in coal mines, a self-advancing support is used in fully mechanized operation. The self-advancing support which supports the hanging roof has at least two hydraulic cylinders or, depending on the size, even four hydraulic cylinders. Problems occurred in the past in arranging the external hydraulic lines at the hydraulic cylinders because the external hydraulic lines were constantly damaged or even destroyed under the rough operating conditions. For this reason, cylinders with bulges were developed, wherein hydraulic ducts were accommodated in the outwardly extending bulge, so that these hydraulic ducts were protected from falling rock. Prior known production of cylinders of this type start with a forged piece which is mechanically machined on all sides. The base is produced separately and connected with the cylindrical part. This known process has to be considered unfavorable with respect to consumption numbers and cycle time.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a process for the production of a cylinder of the type mentioned above which is improved over the known production process with respect to the consumption number, i.e., the ratio of input weight to finished weight, and with respect to the cycle time.
According to the invention, a cropped round ingot or a round continuous-cast ingot is mechanically machined to size, preferably by turning, with a roughness of R
z
≦80 before heating to a temperature between 1250 and 1310° C. After heating, the entire surface is descaled with pressurized water at 300 bar and the ingot is inserted in a mold and pierced in a sharply ascending or increasing manner by means of a mandrel. In so doing, the ingot is lengthened by at least 1.5- to 2.5-times the starting length. The mandrel does not penetrate through the ingot, but rather leaves a base. A lubricant is applied to the mold and mandrel before piercing. This is preferably a mixture of glass powder and pure graphite in a ratio of 1:1, with water glass added. After the pierced piece is ejected from the mold, the outer surface is descaled after cooling. In conclusion, mechanical machining is carried out. Depending on the material and requirements, heat treatment may be necessary and is carried out after the pierced piece is ejected from the mold and before descaling. The heat treatment preferably consists of quenching and tempering in water. The mold is usually arranged vertically, but a horizontal position is also possible.
The advantage of the sharply increasing piercing is that the material is also displaced radially, so that the hollow spaces of the mold forming the bulge are completely filled along a sufficient length. This is conditional upon the mandrel being placed virtually centrically on the ingot. Excessive deviations lead to waste because the bulge is only partially filled. The exact center position of the mandrel is determined in that the mandrel is moved partially into the mold in the cold state and the radial distance from the mold is measured. Accurate adjustment is carried out by means of radial displacement of the mold. In order to assist a centered placement of the mandrel, one portion of the charge ingot or input ingot is mechanically machined to form a cylindrical body and the second portion is mechanically machined to form a conical body, wherein this portion is inserted into the mold. The diameter tolerance of the two portions is in the positive range so as to ensure that the ingot is inserted into the mold in a centered manner.
As a result of the increasing piercing, the mandrel and the mold are highly loaded thermally and it is therefore necessary for the mandrel and mold to be cooled down extensively before the next ingot is inserted. For reasons of dimensioning and with a view to reducing the extent of the final mechanical machining, the conicity or taper of the mold is 0.75%. This is just sufficient to allow the pierced piece to be ejected from the mold by the ejector.
The mold is divided lengthwise and has a cross-sectional contour corresponding to the shape to be produced. In principle, the mold can also be produced in one piece by planing. However, this gives rise to great difficulties and fine machining is problematic. It is simpler to produce a hollow ingot, to divide this hollow ingot longitudinally, and to machine each half mechanically, preferably by cutting. The separately produced base ring is connected with the mold by means of tension bolts so that the machining tool can run out without interference.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
REFERENCES:
patent: 2908385 (1959-10-01), Walker
patent: 3818733 (1974-06-01), Cauley et al.
patent: 4129022 (1978-12-01), Thonnes et al.
patent: 4928507 (1990-05-01), Staat et al.
patent: 5310310 (1994-05-01), Nakatsukasa et al.
Nickel Wilheim
Schlüssel Hans-Jürgen
Schmidt Wilfried
Schmitz Theodor
Cohen & Pontani, Lieberman & Pavane
Cuda Irene
Green Anthony L.
Mannesmann AG
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