Cutting by use of rotating axially moving tool – Tool-support with means to move tool relative to tool-support – To move radially
Reexamination Certificate
2002-04-26
2003-12-02
Howell, Daniel W. (Department: 3722)
Cutting by use of rotating axially moving tool
Tool-support with means to move tool relative to tool-support
To move radially
C082S001200, C408S173000
Reexamination Certificate
active
06655883
ABSTRACT:
The invention relates to a tool holder for use in machine tools, comprising a main body, which rotates about an axis of rotation, and cutter holders which each hold a cutting plate and can be radially adjusted by means of an axially displaceable control rod and coupling means.
Tool holders of this kind are used for turning work, in particular for producing an inner recess, hereinafter called a turned groove. In this connection, tool holders are known which have an axially displaceable control rod which can be driven in an axial movement by means of a machine-side hydraulic or electric servo drive. The axial movement is converted by suitable coupling means, for example via a wedge mechanism that can be actuated by the control rod, into a radial movement of a single cutter holder on which a cutting plate is disposed which comes into engagement with the workpiece to be machined. A tool holder of this kind is known from DE 40 22 579 A1, for example. The latter is for single-cutter machining.
Alternatively, tool holders are already known in which, for the purpose of producing a turned groove, a plurality of cutters are disposed about the circumference of a rotating mount which for its part revolves on a circular trajectory. In this kind of circular milling work, individual cutters successively engage the workpiece which is to be machined.
U.S. Pat. No. 4,275,624 discloses a tool holder in which two cutter holders are simultaneously provided which are disposed at an axial distance from one another and can be adjusted in the axial direction by means of an eccentrically mounted and axially displaceable control rod with an oblique toothing. A cutting tool can be fixed on each of the cutter holders, so that two turned grooves axially spaced apart from each other can be made simultaneously in a workpiece. For each turned groove, only one cutting tool comes into engagement with the workpiece.
Tool holders for single-cutter machining and tool holders with a plurality of cutters for circular machining have the disadvantage that the surface quality obtained with them in the turned groove, and the geometric roundness of the latter, is in many cases unsatisfactory, with the result that re-machining may be necessary. In addition, the turned groove requires a considerable production time.
It is an object of the present invention to form a tool holder of the type mentioned at the outset in such a way that it is possible, within a very short time, to produce a turned groove which satisfies stringent demands regarding surface quality and geometric roundness.
According to the invention, this object is achieved, in a tool holder of the generic type, by the fact that the tool holder has at least two cutter holders which can be radially adjusted between a retracted position and an extended position and whose cutters can be simultaneously brought into engagement with a workpiece in order to produce a turned groove. Using a plurality of cutter holders whose cutters simultaneously engage with the workpiece during machining provides for mutual supporting of the cutters. This results in a higher degree of precision and, consequently, a particularly high surface quality of the turned groove which is produced. Moreover, it is thereby possible to meet very stringent demands in respect of the geometric roundness of the turned groove. In addition, the simultaneous use of a plurality of cutters permits a considerable reduction in the time needed to produce the turned groove. This provides considerable cost advantages for the user, which in turn leads to savings on production units and represents a significant potential for rationalization.
The tool holder preferably comprises three cutter holders disposed about a circumference of a circle and each with an associated cutter. The use of three cutters effects particularly reliable mutual support, and by this means the radial feed can also be increased by a factor of 3 compared to machining of the workpiece with only one cutter, as a result of which, once again, the time needed to produce the turned groove can be correspondingly reduced. In this connection, provision can be made for the tool holders to be disposed uniformly about the circumference. A non-uniform distribution can be particularly advantageous since the non-uniform introduction of force which can thereby be obtained results in strong damping of vibrations.
The radial movement of the cutter holders is produced by the control rod, the movement of which is transmitted to the cutter holders via suitable coupling means. A hydraulic or electric servo drive can be used on the machine side for driving the control rod. However, it is particularly advantageous if the drive of the control rod is effected mechanically. For this purpose, provision can be made for the tool holder to comprise gear means for converting a rotation movement of the main body into an axially oriented reciprocating movement of the control rod. In such an embodiment, the main body has a dual function. On the one hand, the rotation movement guarantees a corresponding rotary movement of the cutters, and, on the other hand, the rotation movement of the main body serves as a drive for the control rod, which in turn produces the radial movement of the cutter holders. Such a configuration has the advantage that on the machine side only a drive spindle has to be provided to which the main body can be coupled in order to obtain a rotation movement, and so a hydraulic or electric servo drive on the machine side can be dispensed with. In this case, the tool holder has a purely mechanical drive system and can therefore be of particularly robust construction.
In order to be able to easily adapt the working stroke of the cutter holders, between their retracted position and their extended position, to the specific conditions of use, it is advantageous if the axial stroke of the control rod is adjustable. For this purpose, depending on the axial stroke which is desired, different gear means can be used for converting the rotation movement of the main body into the axial movement of the control rod.
In a preferred embodiment, the gear means comprise two cam elements which can rotate relative to one another and bear on one another via a control cam which is oriented obliquely with respect to the axial direction. The cam elements can be of annular construction, for example, and can enclose the main body about its circumference, it being ensured that they have a different speed of rotation relative to one another. At least one cam element forms a control cam on which the other cam element bears, and, as a result of the oblique orientation of the control cam, an axial movement is produced by the relative turning of the cam elements which bear on one another.
In this connection, it is advantageous if a first cam element is coupled to the main body via a toothed gearing. In this way, the rotation movement of the main body is transmitted to the first cam element via the toothed gearing.
The toothed gearing can be constructed in the manner of a planetary gear, for example, and can have two planetary wheels disposed on a common axis of rotation, connected rigidly to one another and each meshing with a toothed ring, the toothed rings preferably being oriented coaxially with respect to the axis of rotation of the main body and each surrounding said main body. In this connection, a first toothed ring can be mounted nonrotatably on the main body and thus executes a common rotation movement with the latter, while the second toothed ring has a different speed of rotation in relation to the main body. The first cam element is preferably mounted directly and in a rotationally fixed manner on the second toothed ring. By selecting the desired transmission ratios, on the one hand between the toothed rings and the planetary wheels, and, on the other hand, between the two planetary wheels, the speed of rotation of the second toothed ring and of the first cam element can thus be adjusted.
A rotation movement of the second cam element can be obtained by the fact that it is connec
Howell Daniel W.
Lipsitz Barry R.
McAllister Douglas M.
Wohlhaupter GmbH
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