Abrading – Machine – Rotary tool
Reexamination Certificate
1997-04-18
2001-07-31
Morgan, Eileen P. (Department: 3723)
Abrading
Machine
Rotary tool
C451S278000, C451S282000, C451S430000, C451S115000
Reexamination Certificate
active
06267653
ABSTRACT:
BACKGROUND OF THE INVENTION
The present relates to a grinding device for grinding an end face, especially an annular surface, at the edge of a workpiece bore with a driven grinding tool, the grinding surface of which extends angularly relative to the axis of a guide pin which for a precise introduction into the machined (for example, honed) bore has an identical size (identical dimensions) and which is connected to the grinding tool.
A known device of this kind is disclosed in German patent application 44 41 623 A1 and serves for fine machining a chamfer at the edge of a workpiece bore which serves as a sealing seat for a valve needle. Such valve bores are, for example, provided for injection pumps of combustion engines. They have a very small diameter of only a few millimeters and must be machined very precisely. The end face forming the edge of the bore and surrounding the bore of the workpiece must also be machined very precisely. For grinding or other surface machining of a chamfer, it must be taken into consideration that the truncated cone surface must be positioned exactly concentrically to the axis of the workpiece bore. The known device has a grinding tool with a conical grinding surface for the purpose of surface machining of the chamfer. The grinding tool with its grinding surface is driven so as rotate about the axis of the bore. The shape of the chamfer depends directly on the shape of the grinding surface of the grinding pad which in mass production must be frequently subjected to a trueing or dressing process. Since grinding pads or coatings are in general inhomogeneous, the shape precision and the surface quality of the chamfer in mass production is often unsatisfactory for high-precision workpieces.
Plane honing devices are also known in which the honing tool is displaced with its grinding coating or pad on the surface to be machined. These devices however can not be used for machining processes with limited available space because of their relatively large size.
It is therefore an object of the present invention to embody a device requiring only little space, i.e., space as small as possible, that can produce or machine small end faces, especially annular surfaces at the edge of a bore, with very high precision.
Summary of the Invention
The device for grinding an end face at an edge of a workpiece bore of a workpiece according to the present invention is primarily characterized by:
A driven grinding tool;
A guide pin, connected to the grinding tool, for insertion into the workpiece bore, wherein the guide pin is dimensioned so as to precisely match the workpiece bore;
The guide pin having a central axis;
The grinding tool having a grinding surface extending angularly to the central axis;
Wherein the grinding tool is periodically displaceable transverse to the central axis.
The device preferably further comprises a drive shaft having a rotational axis, wherein the central axis of guide pin is aligned with the rotational axis.
The guide pin is preferably connected to the drive shaft. The drive shaft has a throughbore extending transverse to the central axis of the guide pin. The grinding tool is displaceably guided within the throughbore.
Advantageously, the drive shaft is a telescopic shaft comprising an inner shaft and an outer shaft, wherein the outer shaft is driven and the inner shaft is axially displaceable within the outer shaft.
The outer shaft has a longitudinal slot. The inner shaft comprises a transverse bolt penetrating the inner shaft and guided within the longitudinal slot. The transverse bolt provides a positive-locking connection between the inner shaft and the outer shaft in a rotational direction of the drive shaft.
Preferably, the inner shaft is biased in direction toward the workpiece.
For this purpose, the device further comprises a pressure spring acting on the inner shaft for biasing in the direction toward the workpiece and further comprises a control screw for adjusting the tension of the spring.
Preferably, the inner shaft and the guide pin form an integral part.
Expediently, the device further comprises an eccentric part for periodically transversely displacing the grinding tool relative to the central axis.
Preferably, the device further comprises a driven hollow shaft, wherein the eccentric part is integrally connected to the driven hollow shaft and comprises an eccentric bore that is eccentric relative to a drive axis of the hollow shaft. The grinding tool comprises a holding device positioned in the eccentric bore so as to be displaceable transverse to the drive axis of the hollow shaft.
Preferably, the holding device is a cylindrical slide having opposed end faces that are convex and are supported glidingly on the inner wall of the eccentric bore.
The grinding tool is a plane honing tool comprising at least one honing strip having a honing pad (coating) forming a grinding surface of the honing tool.
The throughbore has preferably a keyhole shape in cross-section including a longitudinal slot projecting into the guide pin. The honing pad of the at least one honing strip projects from the slot toward the guide pin at least at on end of the slot in a longitudinal direction thereof.
The drive shaft is supported within the hollow shaft and the drive shaft and the hollow shaft and the drive shaft and the hollow shaft are operated in opposite directions of rotation.
The device may further comprise a drive pinion, wherein the drive shaft has a toothed section with an outer toothing and the hollow shaft has a toothed section with an inner toothing and wherein the toothed section of the drive shaft is positioned within the toothed section of the hollow shaft. The drive pinion is positioned between the inner and the outer toothings.
The device may also comprise a securing device for the workpiece, whereby the securing device includes a gimbal-mounted clamping device for clamping the workpiece.
The guide pin has at least one guide strip for supporting the guide pin at the inner wall at the workpiece bore.
The grinding surface of the grinding tool may be displaceably perpendicularly to the central axis of the guide pin.
The grinding surface of the grinding tool may instead also be displaceable at an angle to the central axis of the guide pin, wherein the angle is identical to the desired chamfer angle at the edge of the workpiece bore.
Preferably, the grinding tool is advancable in the direction toward the workpiece.
The periodic displacement of the grinding tool transverse to the central axis of the guide pin allows a surface-machining of the end face of workpieces and also the generation of a chamfer at the edge of the workpiece bore with a planar grinding surface, the shape of which is thus not changed by wear and subsequent trueing or dressing operations so that in mass production a very high precision and quality of the machined surface can be achieved. The displacement movement can be realized within a small amount of space so that a minimal constructive height of the entire device results.
During the displacement movement the grinding tool is expediently driven in rotation with a drive shaft, for example, at 2,000 to 6,000 rpm, whereby the periodic displacement is produced with an eccentric part that is preferably a component of the driven hollow shaft with an eccentric bore. Preferably, the hallow shaft is operated counter to the direction of rotation of the drive shaft with 500 to 2,000 rpm. The travel stroke of the transverse displacement is selected such that the grinding surface completely covers the end face to be machined whereby the travel stroke for machining of the surrounding area (edge) of very thin bores is, for example, 0.5 to 3 mm.
REFERENCES:
patent: 2226207 (1940-11-01), Wilhide
patent: 2443489 (1948-06-01), Weynand
patent: 2525119 (1950-10-01), Dunn
patent: 2754642 (1956-07-01), Soulet
patent: 2769287 (1956-11-01), Arp
patent: 2809482 (1957-10-01), Soulet
patent: 4467566 (1984-08-01), Ondrus, Jr. et al.
patent: 4441623 (1995-06-01), None
Aulich Dieter
Klink Ulrich
Schmidt Hermann
Stampfer Richard
Wolfgramm Jörg
Maschinenfabrik Gehring GmbH & Co.
Morgan Eileen P.
Robert W. Becker & Associates
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