Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With separate heating means for work
Reexamination Certificate
2001-05-21
2004-06-29
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With separate heating means for work
C156S084000, C156S085000, C029S447000, C269S2890MR
Reexamination Certificate
active
06755228
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and an apparatus for the thermal clamping and releasing of tools in shrink chucks.
2. Description of the Prior Art
Shrinkage is a known method for the manufacture of high-speed tools for material-removing workpiece machining. Use is made of so-called shrink chucks, which have a tool reception section with an at least zonally thermally widenable tool reception opening for receiving a tool shank, as well as a clamping section provided in a machine spindle for receiving the clamp chuck and which can e.g. be constructed in the manner of a steep taper or a hollow shank taper. Typical diameters of the tools to be shrunk in, e.g. in the form of drilling, milling or grinding tools can be approximately 3 to 6 mm to approximately 30 to 40 mm. For the manufacture of a tool at least one portion of the tool reception section is heated to such an extent that as a result of thermal expansion the tool reception opening is so widened that the tool shank of a tool to be inserted can be introduced. Following the insertion of the tool shank the portion is cooled in such a way that the tool is held by frictional resistance in the tool reception opening shrunk as a result of cooling. Thus, tools are obtained as if in one piece and the connection between the shrink chuck and inserted tool can be released again at any time by shrinking out in that the tool reception section is heated to such an extent that the inserted tool is removable again from the thermally widened tool reception opening. In the present application generally both the tool part to be inserted, e.g. a milling cutter, and the combination resulting from the assembly of the tool part and the shrink chuck is referred to as a tool.
Shrinkage devices are known in which the heating of the tool reception section is performed during shrinking in and out by means of hot air. By means of a separate cooling device equipped with a fan the cooling time can be reduced to approximately 10 minutes to give a temperature suitable for the manual handling of the shrink chuck. Such devices are inexpensive to provide and are particularly suitable for applications where only small numbers of shrink chucks per time unit have to be handled.
During shrinking in and in particular shrinking out of carbide tools by means of hot air devices, as a result of the different thermal expansion coefficients of the tool material and the shrink chuck material problems do not generally arise, but in the case of tools with HSS and steel shanks, particularly when shrinking out problems can occur, because in this case the thermal expansion behavior of the tool material and the chuck material is similar and with slow heating the tool shank can be enlarged to such an extent in the widening tool reception opening that the tool continues to be held by the widening reception opening and cannot be removed or can only be removed by exerting force.
To avoid these problems it has already been proposed to inductively heat the shrink chucks during thermal clamping and releasing. Energy introduction by means of an induction coil surrounding the shrink chuck can take place so rapidly that a temperature rise of shrunk in tools only occurs to a limited extent by heat conduction. Besides permitting the shrinking out of carbide tools, it reliably permits the shrinking out of tools having essentially the same temperature expansion behavior as the material of the typically steel shrink chuck.
A known, inductive shrinkage device is designed as a table-mounted device and has a box-like casing which can be installed on a table and whose top forms the working surface of the device. Above the working surface is raised a column with vertical guides for a coil holder, to which can be fitted an induction coil above the workstation of the device. An integrated pneumatic cylinder moves the column-guided, air-cooled coil into the working position downwards or back into the upper neutral position. The main clamping range of interest with a 6 to 32 mm tool diameter is covered by three different coils, which can be changeably fitted to the coil holder by means of a snap closure. The working surface of the device formed by the top of the casing is designed as a perforated plate through which an air flow produced by a fan located in the casing can be blown from below through the working surface. Besides the work station located below the coil, the work surface carries several circular cooling stations through which air can be blown from below.
For shrinkage purposes a shrink chuck is engaged in a transportable chuck reception sleeve, which is provided with radial cooling ribs and through which air flows from below on installation in the workstation. Then the previously appropriately selected induction coil for heating the shrink chuck is lowered onto the latter and inductive heating is carried out for shrinking in or out. After inserting or removing the tool the coil is raised again. Then the chuck reception sleeve carrying the still hot shrink chuck is placed on one of the cooling stations. To speed up cooling a separate cooling sleeve with cooling ribs surrounding the tool reception section can be installed. The workstation which has been freed below the induction coil can be used for shrinking the next chuck.
The resulting handling of the device has proved to be problematical. It has also been found that the device is only suitable to a limited extent for a rapid passage of higher numbers, because there is a slow overall system heating. Operators have also considered it to be disadvantageous that in part still hot chucks have to be moved in order to achieve a higher throughput.
SUMMARY OF THE INVENTION
The object of the invention is to provide a method and apparatus for the thermal clamping and releasing of tools in shrink chucks, which permit a relaxed, low-fatigue working during shrinking, particularly during the continuous processing of large numbers.
To solve this problem the invention proposes a method for the thermal clamping and release of tools in shrink chucks, a shrink chuck having a tool reception section with an at least zonally thermally widenable tool reception opening for receiving a tool shank and a clamping section for receiving the shrink chuck in a machine spindle, the method comprising a heating of at least part of the tool reception section for widening the tool reception opening and a subsequent active cooling of the tool reception section, the method comprising the following steps:
heating the tool reception section of a first shrink chuck received in a first work station of a shrinking device;
at least one of introducing a tool shank into the tool reception opening of the first shrink chuck and removing a tool from the tool reception opening of the first shrink chuck;
active cooling of the tool reception section of the first shrink chuck received in the first work station;
heating the tool reception section of a second shrink chuck received in a second work station of the shrinking device, the second work station being separate from the first work station of the shrinking device. Further the invention proposes an apparatus for the thermal clamping and release of tools in shrink chucks, a shrink chuck comprising a tool reception section with at least one zonally thermally widenable tool reception opening for receiving a tool shank and a clamping section for receiving the shrink chuck in a machine spindle, the apparatus comprising at least one heating device for heating at least part of the tool reception section and a cooling device for the active cooling of a heated part of the tool reception section, the apparatus comprising
a first work station and
at least one second work station,
wherein a work station is provided for the heating and the active cooling of shrink chucks received in the work station and wherein the work stations and the heating device are movable relative to one another for changing between work stations.
In the case of the thermal clamping or release of tools in shrink chucks
Aftergut Jeff H.
Kelch GmbH & Co. Werkzeugmaschinenfabrik
Knechtel Demeur & Samlan
Rossi Jessica L.
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