Geometrical instruments – Gauge – Collocating
Reexamination Certificate
2003-03-07
2004-09-28
Fulton, Christopher W. (Department: 2859)
Geometrical instruments
Gauge
Collocating
C033S628000, C033S639000, C033S545000, C033S555000
Reexamination Certificate
active
06796050
ABSTRACT:
The invention relates to a presetting device for a tool holder which holds the shank of a rotary tool, in particular of a milling or drilling tool, in an interference fit in a locating opening and releases said shank during heating, in particular by means of an induction heating arrangement.
It is known from WO 01/89758 A1 to hold rotary tools, such as, for example, milling cutters or drills, in a central locating opening of a tool holder exclusively by an interference fit of a sleeve part, forming the locating opening, of the tool holder. The sleeve part of the tool holder, by means of an induction heating arrangement, for example in the form an alternating-current-fed induction coil enclosing the sleeve part, can be heated to such an extent that the shank of the rotary tool can be inserted into the locating opening or removed from it again. The outside diameter of the shank is slightly larger than the nominal inside diameter of the locating opening, so that, when the sleeve part has cooled down, the latter holds the shank in an interference fit.
Conventional tool holders of the above type have a standard coupling, for example a steep-angle-taper coupling or an HSK coupling, by means of which the tool holder is coupled to the spindle of the production machine. In this case, a reference stop surface permits reproducible measuring of the axial position of the rotary tool relative to the spindle or to the tool holder by means of a conventional length-measuring device measuring the distance between a reference stop surface of the spindle or the tool holder and the tip of the rotary tool and thus permits reproducible axial positioning of the tool holder relative to the spindle.
Furthermore, it is known to arrange an axially adjustable positioning stop surface for the tool shank in the locating opening of shrink-fit tool holders of the type explained above. Such a positioning stop surface can be realized, for example, by a screw which projects axially into the locating opening and limits the plunge-in depth of the tool shank in an adjustable manner during the shrink fitting.
Although machine tools permit the subsequent adaptation of the machine setting to the length of the tool-holder/rotary-tool unit, it has nonetheless proved to be advantageous if the rotary tool can be shrunk in a defined axial position relative to the tool holder, in particular a reference stop surface of the tool holder, by presetting the positioning stop surface of the tool holder. Since the period during which these elements are heated is kept as short as possible in order to avoid thermal damage to the tool holder or to the rotary tool, it is desirable for the tool holder not to be adjusted during its heating phase but for it to be adjusted before the shrink-fit operation in such a way that it holds the rotary tool in a predetermined position after the shrink fitting. In addition, the presetting of the positioning stop surface is more accurate when the tool holder is still cold, since no thermal expansions of the tool holder affect the measuring result.
It is the object of the invention to provide a device by means of which axially adjustable shrink-fit tool holders can be preset in the cold state quickly and precisely in such a way that the unit of tool holder and rotary tool has a predetermined axial length after the shrink-fit operation.
In the solution achieving this object, the invention is based on a presetting device for a tool holder which holds the shank of a rotary tool, in particular of a milling or drilling tool, in an interference fit in a locating opening and releases said shank during heating, in particular by means of an induction heating arrangement, and which has inside the locating opening an axially adjustable positioning stop surface for the tool shank. The improvement according to the invention is characterized by the following features:
a) a holder receptacle which holds the tool holder in an axial position and defines an axial opposing reference surface,
b) means for measuring the axial overall length of the rotary tool, and
c) a measuring device which measures the axial distance between the positioning stop surface of the tool holder and the opposing reference surface of the holder receptacle and has a measured-value indicator, the indicated distance value of which can be increased by the measured value of the overall length of the rotary tool.
Such a presetting device, at its measured-value indicator, directly indicates the value of interest in practice between the tip of the rotary tool and a predetermined reproducible position in a holder receptacle. During the presetting measurement, the tool holder sits in a holder receptacle of the presetting device in a manner compatible with practice, and it is sufficient for the length adjustment if the positioning stop surface is adjusted while its distance from the opposing reference surface of the holder receptacle is measured. The presetting device may be separate from the shrink-fitting apparatus inductively heating the tool holder, but preferably forms a construction unit with the shrink-fitting apparatus, in particular when the shrink-fitting apparatus comprises a rotary table on which the tool holder sitting in the holder receptacle is transported successively through a presetting station, in which it is adjusted for the predetermined length, a shrink-fitting station, in which the rotary tool is inserted, and if need be a cooling station, in which the tool holder with rotary tool shrunk in place is cooled again to room temperature.
In a preferred configuration which can be composed of commercially available length-measuring components, provision is made for the measuring device to have a first electric position transducer, which delivers a first distance signal representing the distance between the positioning stop surface and the opposing reference surface, for the means for measuring the overall length of the rotary tool to comprise a second electric position transducer, which delivers a second distance signal representing the overall length, and for the measured-value indicator to comprise means for the summation of the first and the second distance signal and for it to indicate a value representing the sum of the distance signals. The position transducers are preferably digital position transducers, which do not even have to contain measured-value memories, since the rotary tool can remain in the measuring position of the second position transducer during the axial adjustment of the tool holder.
In a variant of the presetting device, a single electrical or mechanical length-measuring instrument is sufficient if the measuring device has two measuring probes which are guided in a displaceable manner in the axial direction of the tool holder relative to the opposing reference surface and of which a first measuring probe is intended for bearing with a measuring surface against the position stop surface of the tool holder, and the second measuring probe is intended for bearing with a measuring surface against an axial end of the rotary tool, while the rotary tool, parallel to the axial direction of the tool holder, bears with its other axial end either on a reference surface of the first measuring probe or on the opposing reference surface, the measuring device measuring the distance between the measuring surfaces of the two measuring probes, and it being possible for the measured-value indicator to be set to zero value indication when the first measuring probe bears on the opposing reference surface and the second measuring probe bears on the reference surface of the first measuring probe or on the rotary tool, respectively. A presetting device of this type, which can in turn be combined with the shrink-fitting apparatus to form a construction unit, provides for a mechanical sum operation, so that here, too, the measured-value indication indicates the sum value of interest in practice.
In order to simplify the manipulation, the first measuring probe and the second measuring probe are expediently guided in a displaceable manner inde
Haimer Franz
Haimer Josef
Kügle Wolfgang
Edwards & Angell LLP
Franz Haimer GmbH
Fulton Christopher W.
Guadalupe Yaritza
Wofsy Scott D.
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