Abrading – Machine – Rotary tool
Reexamination Certificate
1999-05-25
2001-10-30
Banks, Derris H. (Department: 3723)
Abrading
Machine
Rotary tool
C451S251000
Reexamination Certificate
active
06309286
ABSTRACT:
FIELD OF INVENTION
This invention relates to grinding machine.
BACKGROUND TO THE INVENTION
When machining articles to a desired shape it is often necessary to rotate the article (usually termed the workpiece) so that symmetrical machining can be achieved of a given cross section.
Rotation of the workpiece to be machined can be achieved by securing the workpiece into a rotating chuck. However if the workpiece is not centralised correctly within the clamaping jaws of the chuck, it will not rotate in a ‘true’ fashion and machining will be inaccurate.
Alternative methods of transmitting rotation involve the use of a tailstock and a headstock to support the article between centers, the headstock transmitting the rotation, directly or indirectly to the workpiece.
The interengagement between the workpiece and the headstock or driver may be subject to misalignment and offset, which will introduce errors in the machining.
An improved drive transmitting device which will not transmit misalignment or offset to the workpiece is described in U.S. patent application Ser. No. 08/737,974.
SUMMARY OF THE INVENTION
The invention lies in a method of grinding a crankpin of a crankshaft which latter includes a circular flange at one end, comprising the steps of:
mounting the crankshaft between centers;
attaching radially outer regions of the flange to a rotational drive to rotate the crankshaft about its main axis, via a coupling which is torsionally rigid in a plane generally perpendicular to the axis of rotation of the crankshaft but which is readily deformable in other planes to accommodate misalignment;
advancing the grinding wheel to engage a crankpin region of the crankshaft, and
synchronously controlling the position of the grinding wheel whilst the crankshaft is rotated thereby to follow the planetary motion of the crankpin so as to maintain grinding contact between the wheel and the pin.
The advancement and retraction of the grinding wheel is preferably under the control of a computer. In a method as aforesaid, the crankshaft is preferably mounted between headstock and tailstock centres for rotation about its main axis.
The invention also lies in a machine tool (grinding machine) for machining a crankshaft workpiece wherein drive of the latter is provided by means of at least one drive decoupling means, substantially as described in U.S. patent application Ser. No. 08/737,974.
The invention thus provides a grinding machine which is adapted to grind a crankpin region of a crankshaft by synchronously advancing and retracting the grinding wheel as the crankshaft is rotated so the contact is maintained between grinding wheel and crankpin during grinding so as to grind a true cylindrical surface on the crankpin, which includes drive means for rotating the crankshaft, and a coupling means which is torsionally rigid in a plane generally perpendicular to the axis of the crankshaft but is readily deformable in other planes to accommodate misalignment, for correcting the drive means to the crankshaft.
Preferably the drive coupling means a driving member and a driven member which is attachable to the crankshaft so as to rotate the latter and a connecting means for transferring torque the driving and driven members; which comprises a laminated device attached to the driving member via at least one off axis connection and to the driven member by at least one other off axis connection, the connections being circularly spaced one from the other.
In one embodiment the laminations are formed from flexible thin sheet steel, so that the connecting means is torsionally rigid in a plane perpendicular to the drive axis so as to ensure rotation is transmitted reliably to the driven member, and the flexibility of the laminations accommodates any eccentricity developed through misalignment of the driving member and driven member.
In this way the driven member and therefore the workpiece is decoupled from the driving member.
Where the crankshaft and is to be mounted between a headstock and of the grinding machine, the components of the drive decoupling means may be centrally apertured to accommodate the headstock, which can thereby extend axially therethrough to engage one end of the crankshaft.
Preferably the driven member may be provided with radially adjustable means for securing it to the load.
Preferably the securing means is arranged symmetrically and allows centering of the member relative to the crankshaft.
The adjustment may be provided by pneumatic, electrical or hydraulic means so that release and removal of a crankshaft can be performed automatically.
In a particularly preferred embodiment, two drive decoupling means as aforesaid are connected in series, the driven member of the first being connected to the driving member of the second. Such an arrangement allows even greater decoupling to be achieved than if only a single drive decoupling means is employed and permits offset as well as misalignment to be accommodated.
The invention is of value in that it permits an NCR grinding machine to be used to cylindrically grind off-axis crankpins of a crankshaft by synchronously advancing and retracting the grinding wheel as the crankshaft is rotated.
Thus the invention provides a method of grinding a crankpin of a crankshaft mounted for rotation between centres and driven during the grinding process so as to rotate true about its main axis, wherein a rotating grinding wheel is advanced and retracted under computer control in synchronism with the planetary rotation of the crankpin caused by the rotation of the crankshaft so as to maintain grinding contact between the wheel and the pin at all times during the grinding of the pin.
After grinding a crankpin to a desired diameter, the grinding wheel may be retracted and moved axially so as to register with another crankpin on the crankshaft, to enable the latter to be ground.
A grinding machine embodying the invention thus comprises a headstock and tailstock between which a crankshaft can be mounted for true rotation between centres, means for driving the crankshaft, and means for coupling the drive means thereto in a manner so as to remove errors due to offset and misalignment, a grinding wheel which can be advanced and retracted towards and away from a crankshaft when the latter is mounted in the machine and aligned with a crankpin thereof, and a computer for controlling the said advance retraction of the wheel thereby, so as to maintain grinding contact between the wheel and the pin al all times during the grinding of the pin.
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1
is an exploded view of a prior art flexible coupling
FIG.
2
(
a
) is a perspective view of a drive decoupling means as applied to a grinding machine
FIG.
2
(
b
) is a sectional view through the grinding wheel and workpiece as shown in FIG.
2
(
a
)
FIG.
3
(
a
) is a perspective view of the drive decoupling means as applied to grinding crankpins
FIG.
3
(
b
) is a section through the grinding wheel and crankpin as shown in FIG.
3
(
a
)
FIG.
4
(
a
) is an end view a clamping ring for clamping a workpiece to the drive decoupling means
FIG.
4
(
b
) is a section (not to scale) along line A—A of FIG.
4
(
a
).
FIG.
5
(
a
) is an end view of a preferred embodiment for clamping a workpiece within the drive decoupling means
FIG.
5
(
b
) is a section (not to scale) along line B—B of FIG.
5
(
a
) and illustrates an adjustable jaw in more detail.
FIG. 6
in a view of a part of a grinding machine with a housing encasing a drive decoupling device, and
FIG. 7
is a vertical section through the grinding machine housing as shown in FIG.
6
.
REFERENCES:
patent: 4885874 (1989-12-01), Wedeniwski
patent: 5101601 (1992-04-01), Funnell
patent: 5616070 (1997-04-01), Rice et al.
patent: 6038489 (2000-03-01), Pickles et al.
patent: 846517 (1998-06-01), None
Banks Derris H.
Pollack Morris I.
Unova U K Ltd.
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