Abrading – Abrading process – Combined abrading
Patent
1996-01-16
1998-12-01
Rose, Robert A.
Abrading
Abrading process
Combined abrading
451 51, 451 49, 451 66, 451 57, B24B 100
Patent
active
058429115
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
This application relates to International Application No.: PCT/AT93/00119 and was filed pursuant to 35 U.S.C. 1.371.
BACKGROUND OF THE INVENTION
Filed of the Invention
The invention in general relates to a method of making pistons and piston rods as well as cylinders for hydraulic or pneumatic apparatus and, more particularly, to a novel method of successively performing a plurality of surface treatment operations resulting in an exceedingly smooth surface.
It is known by hard-chromium plating to coat pistons for hydraulic or pneumatic cylinders with a layer of chromium. However, chrome plating has been found to be prone to deteriorate and in time leads to the formation of rust and rapid wear of the pistons and seals. It is also known by anodization to provide aluminum components with a wear-resistant surface coating.
Heretofore, hard-anodization of piston surfaces, for instance, has not been considered to yield satisfactory results because of the micro-porosity and corresponding roughness of the resultant surface which absolutely mitigate against its utilization as a sliding surface. As regards pistons and piston rods in particular, such a rough surfaces would damage the cylinder seals.
Attempts have repeatedly been made to reduce the rough-ness of the coating such as, for instance, by compressing and sealing of the pores in a hot water bath, or by grinding with a grinding powder. It has not been possible, however, to come close to the surface quality required for use with pistons or piston rods, as the case may be.
OBJECTS OF THE INVENTION
The invention is directed to providing a method which ensures long life of pistons or piston rods, as the case may be, and of cylinders of hydraulic or pneumatic apparatus. The method in accordance with the invention is characterized by hard-anodizing the sliding surface of a precision-finished semi-fabricated cylindrical component and by rotating the hard-anodized component about its axis and by treating the resultant sliding surface thereof to a plurality of successive grinding operations with two-dimensional grinding media of differing decreasing grain sizes, whereby each grinding operation is carried out until any dust formation ends and whereby buffing takes place during the final grinding operation until adherence of the two-dimensional grinding medium.
SUMMARY OF THE INVENTION
With the method in accordance with the invention, it has now become possible for the first time to manufacture pistons and piston rods as well as cylinders made of an aluminum alloy having a sliding surface with a roughness depth R.sub.t of 0.3 .mu.m. Such a sliding surface smoothness avoids any possibility of seals deteriorating and ensures a substantially increased useful life as compared to conventional chrome-plated components.
The method in accordance with the invention makes it possible to provide uniform surface qualities in the most diverse kind of initial surfaces substantially regardless of their initial roughness.
It has been found to be particularly advantageous to execute five grinding steps with type P 100, P 150, P 280, P 400 and P 999 grinding webs, P 100 being a grinding web made with a sieve having 100 meshes per inch. These values are optimized; departure from these values will lead to a deterioration of surface quality.
A further optimization is obtained by rotating the hard-anodized component during the grinding operation at about 2,500 rpm, and by an engagement pressure of the grinding medium of about 50 N.
An especially long service life of the pistons and piston rods as well as of the cylinders results from using AlMgSi 1 alloy as the material for manufacturing the semi-fabricated component and from a depth of anodization of 50 to 60 .mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
The method in accordance with the invention will now be described in further detail on the basis of an embodiment and a piston rod made in accordance therewith. In the descrip-tion, reference will be made to the drawings, in which:
FIG. 1 de
REFERENCES:
patent: 4599827 (1986-07-01), Goodwin
patent: 5643054 (1997-07-01), Bach et al.
patent: 5674111 (1997-10-01), Harada et al.
Hormann Karl
Nguyen George
Rose Robert A.
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