Tool changing – Including machine tool or component – Rotary spindle machine tool
Reexamination Certificate
2000-11-15
2002-02-19
Briggs, William (Department: 3722)
Tool changing
Including machine tool or component
Rotary spindle machine tool
C279S004110, C279S900000, C483S001000, C483S054000, C483S055000
Reexamination Certificate
active
06348029
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a machine tool for workpiece machining, including triaxial machining of workpieces and more particularly to a machine tool with at least one machining unit, which has at least one work spindle which can be rotatably driven around an axis of rotation, provided with a revolver head that has a plurality of driven spindles, which carry a tool in a tool carrier each and are displaceable in a work space in the X, Y and Z directions and with at least one tool magazine arranged in the work space.
BACKGROUND OF THE INVENTION
A machine tool of this type with a revolver head and a tool magazine arranged in the work space, which has the features noted above, is shown in EP 433 248 A2.
Machine tools with a revolver head makes possible a rapid tool change by simple rotation of the revolver head. However, the number of tools arranged on a revolver head is usually limited to eight tools. It is common practice for repetition work, e.g., in so-called CNC-controlled machining centers, to replace the tools in one operation manually when all eight tools arranged on the tool revolver have become worn or otherwise unfit for use. Even though the number of available tools can be increased by using a plurality of tool revolvers in the case of the use of multi-station machine tools, this is, of course much more complicated and expensive.
A machine tool with a revolver head for mounting tools with a coaxial drum magazine for storing additional tools and with an automatic means for delivering the tools from the magazine into a working position at the revolver head has been known from DE 27 37 225 A1, where a separate lifting means for transporting the tools from and to the drum magazine is provided in the revolver head. This additional lifting means as well as the concentrically arranged drum magazine proper require relatively much space. In addition, displaceability of the revolver head in the X, Y and Z directions is not provided here.
Another machine tool with automatic tool change is described in DE-OS 14 77 429, in which the tool spindle and the tool magazine are arranged on a common carriage and the magazine holds the tools by means of the spindle at right angles to the spindle axis. A separate gripper-type change mechanism is likewise provided for the tool change here, where the gripper first removes the tools from the magazine in the direction of the spindle axis, then pivots them into the spindle axis and finally pushes them again into the spindle. This type of tool change is also complicated and time-consuming.
A hydraulic clamping device for the detachable precision holding of machine parts, which is also called a hydraulic expansion clamping device, has been known from EP 890 402 A1. This has axially parallel, especially cylindrical holding surfaces with wall parts which can be bent out elastically, which define a hollow space, which is connected to at least one hydraulic pressure source. The pressure source comprises a piston, which is moved by a manually actuated hexagon socket screw arranged in a threaded hole of the housing. Automatic adjustment of the hexagon socket screw is not provided for here and would also lead to increased wear and, because of the complicated coupling of the screwing tool, to a slowdown of the tool change process.
SUMMARY AND OBJECTS OF THE INVENTION
The basic object of the present invention is therefore to provide a machine tool of this type that makes possible a rapid, automatic tool change between the tool carrier on the spindle and a tool magazine within the work space.
According to the present invention, the tool carriers of the spindle and of the tool magazine are arranged in the work space for the tool change and are preferably moved from their longitudinal direction from one tool carrier into the other tool carrier by means of an actuating means arranged at the tool magazine, which preferably comprises only a lifting cylinder and a guide sleeve. A precision tool carrier, which comprises a hydraulic expansion chuck according to the present invention and makes possible a very high accuracy of fit, is arranged according to the present invention at the spindle.
One peculiarity is that the individual tools do not have intermediate holders of their own, with which the tools are usually accurately positioned at the tool spindle. The tools are moved according to the present invention without intermediate holder between the magazine and the spindle. The elimination of the so-called intermediate holder is made possible by the fact that the spindle of the revolver head can be positioned exactly at the tool carrier of the tool magazine and the tool shank can be pushed in a correctly fitting manner into the tool carrier of the spindle preferably with a simple change slide.
Furthermore, provisions are made according to the present invention for the hydraulic expansion chuck to be clamped and released automatically by means of the spindle. To do so, a ring, which actuates at least one linearly movable hydraulic piston to change the pressure of the hydraulic expansion chuck, is rotatably movable on the tool carrier of the spindle. To actuate the hydraulic piston, the ring performs a movement relative to the tool carrier of the spindle by the spindle being rotated with the tool carrier and the ring being fixed on the tool carrier of the tool magazine by means of a rotation prevention device. The drive of the spindle is thus used in a simple manner to change the pressure of the hydraulic medium by means of the hydraulic piston and to release or clamp the hydraulic expansion chuck. The tool change can consequently be performed automatically and within a very short time and without manual intervention in the closed work space.
To change the pressure in the hydraulic space, it proved to be favorable to push the hydraulic piston to the outside by spring force, on the one hand, and to move it inward against the spring force by actuating the ring, on the other hand.
The ring arranged rotatably movably on the tool carrier may consist of a threaded ring or a tensioning nut and be moved in a defined manner in the axial direction by its rotary movement relative to the tool carrier and to also one or more hydraulic pistons in the axial direction, which ensure a change in the pressure at the hydraulic expansion chuck. Instead of a threaded ring, which can be moved axially continuously and over any desired number of revolutions, it is also possible to use an eccentric ring, which can move the hydraulic piston toward the center of the hydraulic expansion chuck during a rotary movement by, e.g., 90°. As an alternative to this, the releasing and clamping of the hydraulic expansion chuck may also be brought about by means of a slot on the chuck and changer housing. The hydraulic piston is preferably arranged radially in this case, but it may also be directed inwardly at any desired oblique angle.
The use of the hydraulic expansion chuck has the advantage that the tools can be mounted without clearance with a very high repeating accuracy of approx. 0.002 mm.
The tool magazine is designed especially as a round magazine with a central axis of rotation and a rotating drive belonging to it, wherein preferably four or five tool carriers are arranged on a common bridge axially in parallel, distributed over the circumference, with an actuating device acting in the direction of the axis of rotation acting centrally on the bridge. This actuating device, which is expediently designed as a lifting or hydraulic cylinder, has a change slide, which is mounted displaceably on guide elements fastened to the housing. This change slide is directly connected to the central lifting cylinder and via the bridge to the tool carriers arranged distributed over the circumference. The bridge extends at right angles to the axis of rotation of the tool magazine and has arms which extend to the outside in a star-shaped pattern and on which at least two gripping arms and/or plate springs each, which are laterally in contact with the tool under pretension are fastened
Bauer Walter
Baumbusch Frank
Briggs William
McGlew & Tuttle P.C.
Witzig & Frank GmbH
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