The invention relates to a tool-driving device that is particularly designed for use in machine tools or in machining units of machining centers, and has at least one machine spindle that is seated to move.
Machine tools are used especially for material-removal processes, such as boring, milling, turning on a lathe, etc.
The tool is inserted into a corresponding tool receptacle that is secured in the work spindle of the relevant machine tool. Various tool receptacles are available.
During the machining process, the work spindles are driven by associated drive apparatuses. Control devices, which can include expanded electronic circuits or execution programs, are provided for controlling the spindle movement, notably its rotation and/or adjustment.
The control device establishes the rpm of the spindle within an rpm range. This range is inherently limited. It may be that, particularly for very small tool diameters or for other reasons, rpms outside of the rpm range of the spindle are required.
It is the object of the invention to provide a tool-driving device that expands the application range of a machine tool or machining unit, preferably with as little intrusion as possible into the existing machine control.
This object is accomplished with a tool-driving device having the features of claim 1.
The tool-driving device of the invention has a spindle insert, which can preferably be clamped, fixed against relative rotation, in a machine spindle and can support a tool for machining workpieces. A coupling device serves to secure the spindle insert in the machine spindle. A drive that is supplied by a drive source located outside of the spindle insert, and can be controlled by a control device, is provided for driving the tool. The drive is effected by way of a coupling element that can be connected to the supply lines of the drive. The drive is controlled as a function of the movement of the machine spindle; the tool-driving device is provided with a detection device for detecting this movement.
From the spindle movement, the detection device obtains a signal that characterizes, for example, the rpm, and is used as an input signal for the control device for controlling the drive, and therefore the movement, of the tool. The detection of the rpm requires no access to the machine control, especially if no control signals originating from the machine control are necessary. The control device is separate from the other machine control, and is therefore independent and self-sufficient.
If desired, the power supply can be effected by the tapping of the machine control or the drive source of the machine tool. A dedicated drive source can, however, also be provided for the power supply.
The tool-driving device permits the increase of the rpm of the machine spindles above and beyond the capabilities of the machine spindle. Unlike in a passive accessory gear, in this instance the additional supply of power in the drive of the tool permits the conversion of an output that exceeds the output of the machine spindle. The maximum torque can be completely retained while the rpm is increased.
The spindle insert has a coupling device, e.g., a 7/24 taper shank, which permits a secure, detachable connectionxe2x80x94fixed against relative rotationxe2x80x94with the machine spindle. It also has an essentially cylindrical, one- or multiple-part housing, inside which the drive is disposed.
If material-removal operations are to be executed with a rotating tool, the drive is embodied as a rotary drive. A motor, e.g., an electric motor, serves to drive the tool. DC motors, synchronous motors or asynchronous motors can be used for a single- or polyphase alternating current. Hydraulic or pneumatic drives, with which rotational or axial movements of the tool can be attained, can also be used. The motors can be connected to the tool directly, or via a gear in a driving arrangement.
In a preferred embodiment of the invention, a receiving apparatus is provided for receiving the tool; the apparatus has a tool spindle, into which the tool is clamped, fixed against relative rotation. The tool spindle preferably has a conical inside shape. The tool spindle is then formed by a rotatably-seated shaft, and projects out of the housing. The shaft is connected to a rotating part of the motor (internal or external rotor) so as to be fixed against relative rotation. The shaft and the tool spindle are preferably embodied to rotate symmetrically relative to an axis of rotation established by the machine spindle. The tool spindle can, however, also support a quick-clamping element, a jaw chuck or the like.
At least one slip ring, which is mounted to the outside of the housing and is electrically insulated from it, and can be brought into engagement with an associated sliding contact of the coupling element, is provided for supplying power to the electric motor. When the machine spindle rotates, the sliding contacts slide along the slip rings, thereby assuring the power supply to the drive. Rollers can also be used instead of sliding contacts. The supply can also be effected contactless, e.g., with transformers.
The slip rings are preferably disposed on a conical part of the housing whose diameter increases starting from the machine spindle. The slip rings therefore have different diameters. The smallest diameter is larger than that of an arbitrary part of the coupling device. Thus, the spindle insert can be inserted into the machine spindle without altering the position of the contact set. The contact set can then be rigidly secured to the machine tool, in which case it is disposed at a slight incline, corresponding to the incline of the conical housing part. The insertion of the spindle insert produces the contact between the slip rings and the sliding contacts. The contact set can also be seated to be adjusted, and/or can be separate.
The safety of the tool-driving device is increased when voltage is only applied to the sliding contacts during the machining process. If the detection device detects rpms that are at least as high as a defined threshold value, preferably 30 rpm, the current supply to the sliding contacts is enabled, for example, by the automatic closure of a switch. The circuit is opened at rpms below the threshold value.
Contactless, magnetic or optical methods are preferred for rpm detection. For example, a metal part connected to rotate with the spindle insert or the machine spindle can serve to induce a short voltage pulse in a stationary coil with each rotation.
In an advantageous embodiment, the detection device has a signal generator, particularly a light source, and a signal receiver, particularly a light sensor. The detection device is preferably adjustably mounted to the machine tool, for example to the spindle head that guides the machine spindle. A marking, such as a narrow metal plate, that reflects the light emitted by the light source is secured to the tool coupling or the machine spindle. A signal that is thereby generated, and characterizes the rpm of the machine spindle, e.g., a pulse signal that is proportional thereto, is then transmitted to the control device.
A circular clamping body having different visual properties from the location where it is to be secured can serve as a marking. The clamping body can have a gap or a recess.
The passage of the gap or recess in front of the sensor generates the signal.
Markings that effect the generation of a plurality of signals with each rotation can also be provided. In the simplest case, the markings can be equidistantly spaced and provided on, for example, an adhesive strip.
The control device utilizes the signals arriving from the detection device to generate a corresponding drive signal for the drive. Hence, the rpm range of the tool can be expanded with the device of the invention. Existing machine tools can therefore be rendered more versatile without its mechanical or electronic components being disturbed.
The control device can be integrated into the spindle insert, or accommodated separately. It can also be controlled by programs running on a computer. A console can be provided for the user.
At least one supply line for a cooling fluid or compressed air is preferably provided in the tool-driving device for cooling the tool, as is an outward-oriented nozzle, which is preferably pivotable and comprises plastic, for example. At the same time, the nozzle can conduct heat out of the tool-driving device.
Further advantageous details about embodiments of the invention ensue from the dependent claims, the drawing and/or the associated description.