Slide grinding machine

Abstract

A slide grinding machine having a turntable and a work container rotated by the turntable has an air pressure operated automatic gap setting feature having a zero gap width reference value to adjust the gap width between the turntable and the work container.

Claims

1. A slide grinding machine having a work container and a turntable, wherein the gap width of a ring gap located between the turntable and the work container is set automatically, comprising: a compressed air device with which the gap can be acted on by compressed air along a total periphery thereof for determining a gap width of zero; a pressure sensor which measures the air pressure arising in a region of the gap on a pressure side on applying compressed air to the gap; an actuating drive with which the turntable and the work container can be moved toward one another and away from one another in relation to one another; a control and regulation device in which a relative position of the turntable and of the work container can be stored as the reference value for a gap width of zero which is present when air pressure measured by the sensor has reached a predefined limit value; and a regulation which is implemented in the control and regulation device and with which a desired constant gap width relative to the stored relative position can be regulated in dependence on a temperature measured in the region of the gap during the operation of the slide grinding machine with the help of the actuating drive.

2. The slide grinding machine in accordance with claim 1, which is adapted to carry out a method for the automatic gap setting, wherein the gap width of the ring gap located between the turntable and a work container is set by the regulation.

3. The slide grinding machine in accordance with claim 1, wherein the turntable is driven via a belt drive; and wherein a shaft of the turntable is movable relative to the work container with the aid of the actuating drive.

4. The slide grinding machine in accordance with claim 1, further comprising a displacement sensor which is adapted to detect a positional difference of the turntable relative to the reference value.

5. The slide grinding machine in accordance with claim 4, wherein the displacement sensor is integrated into the actuating drive.

6. The slide grinding machine in accordance with claim 1, further comprising a temperature sensor which is adapted to determine the temperature in the region of the gap and forwards the temperature as a regulating parameter to the control and regulation device.

Description

(1) The present invention will be described in the following purely by way of example with reference to an advantageous embodiment and to the enclosed drawings. There are shown:

(2) FIG. 1 a part sectional view of a slide grinding machine in a plane which runs through the axis of rotation of the turntable;

(3) FIG. 2 an enlarged part sectional view of the gap region; and

(4) FIG. 3 a further enlarged part sectional view of the gap region.

(5) The present invention will be described in the following with reference to a slide grinding machine in which the turntable is moved relative to the work container and the ring gap is acted on by compressed air from below, i.e. from outside the internal volume of the work container. The invention could, however, also generally be implemented in that the work container is moved or in that the ring gap is acted on by compressed air from above.

(6) FIG. 1 shows in a part section a slide grinding machine having a work container 10 which is open at its upper side and which is closed by a turntable 12 at its lower side, with a peripheral ring gap 18 being present between the lower container margin 14 and the margin 16 of the turntable 12. The size of the ring gap 18 varies in dependence on the machine size and on the demands and can lie in the range from approximately 0.2 mm to approximately 0.8 mm. A respective ring gap with a gap width of zero is shown in FIG. 1 to FIG. 3.

(7) The work container 10 is fixedly mounted on a machine frame (not shown), whereas the turntable 12 can be rotated about its center axis A with the aid of a motor (likewise not shown). For this purpose, the shaft 20 of the turntable 12 is rotatably supported in an axial bearing 22 mounted on the machine rack, with the shaft 20 being able to be moved with the aid of a dual action hydraulic cylinder 24 along the axis of rotation A in the direction of the work container 10 and away from it. In other words, with the aid of the actuating drive realized by the hydraulic cylinder 24, the turntable 12 can be moved relative to the work container 10 so that the turntable and the work container can be moved toward one another and away from one another in relation to one another.

(8) A bearing part 26 is located beneath the turntable 12; it is fixedly connected to the machine frame and forms a closed space together with the turntable 12 through which closed space liquid can flow off with an open ring gap 18. The space 28 is connected to a liquid container 30 in which a transducer 32 is located which is used as a liquid level sensor in the operation of the slide grinding machine, but which is also able to measure the air pressure present in the space 28. The space 28 can be vented via a valve—not shown—but is closed in an air-tight manner with a closed ring gap and a closed valve. The space 28 can be acted on by compressed air via an air pressure connection (not recognizable in the drawing) so that the ring gap 18 is also acted on by compressed air. An air pressure thus arises in the interior of the space 28 with a closed ring gap 18 which can be measured with the aid of the transducer 32.

(9) As FIGS. 1 and 3 further illustrate, a temperature sensor 34 is introduced in the work container 10 in the region of the ring gap 18 and its front end terminates substantially flush with the container wall or with the polyurethane coating of the work container 10 hatched in FIGS. 2 and 3 in the region of the ring gap 18. In this manner, the temperature present in the region of the ring gap 18, for example the temperature of a process liquid conducted through the ring gap can be measured very exactly and a conclusion can then indirectly be drawn from it on the gap size change which results by the temperature change.

(10) To detect the stroke of the turntable 12, the actuating drive 24 is provided with a deflection sensor 36 which measures the stroke of the turntable 12 parallel to the axis of rotation A. In this manner, the axial spacing between the work container 10 and the turntable 12 can be measured very exactly and the gap width can thus also be set. The rotational drive of the turntable 12 takes place via a belt drive 38, with a drive via a chain or the like also being conceivable. The belt drive 38 is driven by the drive motor (not shown) and drives the turntable 12 via a belt pulley 40 which is fastened to the shaft 20. On an axial displacement of the shaft 20 with the aid of the hydraulic cylinder 24, the belt drive 38 compensates the axial stroke which occurs.

(11) The method in accordance with the invention for the automatic gap setting with the aid of a regulation will be described in the following.

(12) To determine a reference value for the gap width of zero, first the work container is emptied and any liquid located in the space 28 is removed or drained off. Subsequently, the space 28 is acted on with compressed air via the compressed air connection with an open gap so that the ring gap 18 is also acted on evenly with compressed air over its total periphery on its pressure side, i.e. in the region of the space 28. The supply pressure can here amount to 300 mbar, for example. Since the gap is still open, the compressed air first escapes in the region of the space 28 (shown hatched in FIG. 2) through the ring gap 18.

(13) Subsequently, with otherwise closed venting valves, the gap width is increasingly reduced in size in that the hydraulic cylinder 24 is actuated. As the ring gap is increasingly closed, the air pressure within the space 28 increased, which can be detected by the sensor 32. If the air pressure measured by the sensor 32 on the pressure side of the gap 18, i.e. in the space 28, has reached a predefined limit value of, for example 150 mbar, the hydraulic cylinder 24 is stopped in its position and the position determined by the displacement sensor 36 is stored in the control and regulation device. A reproducible parameter for the zero frequency of the measurement and regulation system is hereby found so that, starting from this reference value, the desired gap width can be set in that the hydraulic cylinder 24 is actuated in the opposite direction so that the turntable 12 is lowered a little downwardly.

(14) During the following slide grinding, the position of the turntable thus set in the axial direction can be permanently maintained in that the temperature sensor 34 measures the temperature present in the region of the gap 18 and adjusts the turntable 18 relative to the determined reference value (zero point) by a predefined value on a temperature increase or on a temperature reduction. It was determined in practical experiments in this respect that the gap dimension changes by a constant value on a temperature change of, for example, 1° C. This change of the gap dimension can be corrected continuously, automatically and permanently by a corresponding regulation in that the hydraulic cylinder 24 is correspondingly actuated by the control and regulation device. During operation, the measuring and regulating device continuously measures the temperature present in the gap and accordingly adjusts the gap dimension by actuating the actuating drive 24 on a temperature change. The gap dimension can hereby be kept constant with a precision of approximately 25 μm.

(15) The determination of the reference value for the gap width of zero can be repeated with reference to predefined criteria, for example after reaching a defined operating time of the slide grinding machine or on an exceeding of a predefined temperature limit.

(16) It must be mentioned in addition that in the region of the hydraulic supply of the hydraulic cylinder 24 (a pneumatic control or also a stepped motor could generally also be used as an actuating drive), a pressure regulation valve and an additional pressure sensor are present which are present as redundant monitoring devices in addition to the pressure sensor 32 if the latter should have a malfunction. In addition, the pressure sensor in the region of the hydraulics serves for the exact control of the stroke of the hydraulic cylinder 24.