Steady rest

Abstract

To provide potential provision of a more accurate and simpler detection of the position of a pressure element, and potential further alleviation of a problem of penetrating liquid.SOLUTION: By use of a distance sensor that detects the position of a pressure element and is drained via a drain hole, the drain hole during operation is closed by means of a sealing air-actuated discharge valve, so that during the operation the sealing air cannot escape through the drain hole but in a rest state any liquid that has still penetrated drains off through the drain hole.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The invention relates to a steady rest for holding a workpiece on a machine tool, which has an operating piston which can be actuated in a substantially vertical direction, on either side of which two angle levers are arranged, which operating piston cooperates with the angle levers via pressure elements inside a housing, in which a cut-off air supply channel is assigned to prevent the ingress of liquids.

[0002] Such a steady rest is already known from DE 10 2007 025 924 C1. As a distance transmitter for detecting the position of the pressure element and thus for monitoring the clamping position of the steady rest, it provides a cable which can be wound up and unwound by means of a fixed-position winding device. The position detection takes place with reference to the pivot position of the winding device, which can be picked up via a potentiometer. In relation to the resistance measured by the potentiometer, the respective clamping position of the actuating piston can be deduced.

[0003] The steady rest consists of three holding elements which approach the workpiece to be clamped from three sides. During the clamping process, an operating piston is actuated, which has a middle holding element which approaches the workpiece from its underside. On both sides of the operating piston, two angle levers are provided, which are supported so as to be pivotable about a pivot axis and can be moved from an open position to a closed position by raising a pressure element connected to the operating piston. For this purpose, the pressure element has a rolling surface on which a rolling means is supported on the end of the angle lever which is located in the housing, via which the angle lever can be displaced in relation to the clamping position of the operating piston.

[0004] In such an arrangement, the winding device for the cable is located outside the housing in which the operating piston cooperates with the angle lever inside. In this arrangement, splashes of water occurring within the scope of machining of the workpiece, for example cooling lubricant, can penetrate into the housing. Although the cable does not indeed exit the housing at its lowest point, it nevertheless turns out that liquids can escape from the housing downwards along the cable and penetrate into the winding device, causing continuous damage to the latter.

[0005] Starting from this background, the problem underlying the present invention is to propose a steady rest for holding workpieces, which allows precise position detection and at the same time avoids damage and injury from infiltrating liquids as far as possible.

[0006] This problem is solved by a steady rest for holding a workpiece according to the features of the independent claim 1. Important refinements of such a steady rest can be seen from the dependent claims which follow claim 1.

[0007] According to the invention, a steady rest for holding a workpiece on a machine tool is specified, which comprises a substantially vertically actuable operating piston, on either side of which two angle levers are arranged, which actuate the operating piston via a pressure element inside a housing with which the angle levers are associated, and in which a cut-off air supply is assigned to prevent the ingress of liquids. Such a steady rest has the advantage over the already known prior art in that the operating position of the pressure element is assigned to the housing below the lowest position of the pressure element and can be detected by means of a distance sensor, and the front cavity of the distance sensor has an outlet hole which can be closed via an air-operated outlet valve for draining the front cavity.

[0008] This has the advantage that during operation of the machine tool, i.e. while liquid may be generated, a shut-off pressure, preferably in the range of 0.5-1.0 bar overpressure, is applied to the housing, which prevents liquid from entering the housing. If the shut-off air is switched off after operation, any liquid still present may indeed enter further into the housing, but it will collect at the lowest point and can be drained there. Such a lowest point may be, for example, the position of the distance sensor, since the distance sensor must be arranged further below the lowest travel position of the pressure element in order to be able to detect the total travel distance of the pressure element.

[0009] On the one hand, the upstream cavity of the distance sensor, which allows for an accurate measurement of the position of the pressure element, and on the other hand can be liquid-tightly shielded towards the housing, can serve as a collection tank into which the generated liquid can flow and then flow out via the outflow hole, so that it is guaranteed that no liquid is present in front of the distance sensor.

[0010] A distinction must be made between a rest situation and an operating situation. In the rest situation, the liquid that is generated may flow into the fore-cavity, which may preferably be, but does not have to be, the absolute low point of the housing cavity. A separate outlet may be provided at a lower point. In a pressure-free state, i.e. when no blocking air is present, the outlet hole is opened by the outlet valve, so that the liquid can flow out of the fore-cavity.

[0011] In contrast, during operation, the blocking air is brought into the housing, which generates an overpressure in the housing. At the same time, the pressure of the blocking air is applied to the outlet valve, which operates the outlet valve. The blocking air cannot escape through the outlet hole, which serves to prevent liquid from entering the housing. In particular, the pre-cavity remains empty, so that the measurement of the distance sensor is not impaired.

[0012] In a specific refinement, it may be specified that the distance sensor is oriented parallel to the actuating piston and that the pressure element has a reflecting surface located opposite the distance sensor for reflecting the distance signal emitted by the distance sensor. Such a configuration allows contactless detection of the distance between the distance sensor and the pressure element by a wide variety of sensors. What can be considered as preferred in such an arrangement is that the reflecting surface is oriented and configured in a straight manner so that the signal emitted by the distance sensor is reflected back to the distance sensor and the reflection is incident thereon with sufficient strength.

[0013] With regard to the configuration of the outlet valve, it can also be assigned a spring-operated shutoff piston which opens the outlet orifice in the absence of pressure. In this configuration, the shutoff piston has an enlargement on the head side, and a compression spring is arranged between this enlargement and the abutment surface. In this configuration, the shutoff piston can only be operated against the force of the compression spring.

[0014] Preferably, the shutoff piston can be assigned a separate shutoff air port on the operating side, via which an air supply can be provided, which can push the shutoff piston against the spring force of the compression spring into the outlet hole, thereby closing the outlet hole, preferably airtight. This has the advantage that sufficient pressure for operating the outlet valve can be guaranteed by means of the separate air port.

[0015] However, instead of such an arrangement, it is possible for the shut-off piston to be connected on its operating side to the housing part to which the shut-off air is supplied, which would certainly likewise require the supply of shut-off air to the valve, but would not necessarily require a separate line.

[0016] Several advantages can be obtained if the distance sensor, the pre-cavity, the outlet hole and the outlet valve are accommodated in a drainage housing that can be detached from the housing. Such an arrangement allows for a simple exchange of the position detection device by replacing the entire assembly. This makes it easier to eliminate possible malfunctions.

[0017] Preferably, the housing may be assigned at least one cut-off air port at least at a local geodetic low point of the housing cavity formed in the housing. Since liquid collects at the lowest point due to gravity, it may be advantageous to provide the cut-off air exactly there, since otherwise the cut-off air would not be able to drain the already entered liquid again. Also at such a point, a separate, closable outflow line may be provided.

[0018] Particularly advantageously, the housing or the drainage housing can be assigned a cut-off air port in the area of ​​the distance sensor, preferably in the area of ​​the front cavity of the distance sensor. If the cut-off air is brought directly into the area of ​​the distance sensor, this ensures that the liquid flowing further inside the housing is directed away from the distance sensor. This is particularly advantageous if the distance sensor itself is located at the lowest point of the housing.

[0019] In a specific configuration, the distance sensor may be an ultrasonic sensor, which is particularly suitable for applications of the present invention where there is a high risk of the distance sensor being wetted by liquid, since such a configuration allows for accurate position detection and is less susceptible to failure due to minor contamination than, for example, optical sensors.

[0020] The above-mentioned present invention will now be described in detail with reference to an embodiment. [Brief description of the drawings]

[0021] [Figure 1]FIG. 2 is a cross-sectional side view of a steady rest for holding a workpiece with an adjacent drainage housing; [Diagram 2] FIG. 2 is a detailed view showing the drainage housing of the steady rest shown in FIG. 1 in an operational state with the spill valve closed. [Diagram 3] FIG. 3 shows the drainage housing shown in FIG. 2 in an alternative rest state with an open spill valve.

[0022] In the steady rest 1 shown in FIG. 1, an actuating piston 7 is provided for actuating two laterally located angle levers 6 via a pressure element 8. In FIG. 1, the steady rest 1 is in a closed clamping state, in which the workpiece 2 is fixed between the holding surface formed by the holding element of the actuating piston 7 and the angle levers 6. In order to be able to detect the clamping position of the steady rest 1 as a signal for the tool control, an ultrasonic sensor 12 is provided as a distance sensor, which detects the distance to the reflecting surface 9 and thus makes it possible to deduce the position and clamping state of the pressure element 8. The pressure element 7 actuates the angle levers 6, so that all clamping states of the steady rest 1 can be determined.

[0023] When the workpiece 2 is machined in this position, liquid, for example due to the use of a cooling lubricant, can get into the housing 3 surrounding the pressure element 8 and the lower area of ​​the angle lever 6 and the operating piston 7. Since the ultrasonic sensor must be located below the lowest deflection of the pressure element 8 in order to be able to detect each possible position of the pressure element 8, the intruding liquid can collect in the pre-cavity 13 arranged in front of the ultrasonic sensor 12 and thus impair the measured value of the ultrasonic sensor 12. Thus, via the cut-off air port 5 cut-off air is brought into the housing cavity 4 formed by the housing 3, as a result of which an overpressure is generated in the housing 3. This makes it possible to largely, if not completely, avoid the intrusion of liquid at least during operation.

[0024] In order to also remove any liquid that still penetrates into the housing after the cut-off air is cut off, a drainage housing 11 is provided at the lowest point, which is shown enlarged in FIG. 2 as a detailed view of FIG. 1. The drainage housing opens into the housing 3 by means of a front cavity 13. Through the front cavity 13, the ultrasonic sensor 12 transmits its distance signal 10, which is reflected by the ultrasonic sensor 12 again. By the time lag of the reflection, the distance of the pressure element 8 to the reflecting surface 9 can be deduced. From the front cavity 13, a downwardly sloping outlet hole 14 extends outwards, which is closed by an outlet valve 15. This is the operating state in which the ingress of the cut-off air creates an overpressure of 0.5-1.0 bar in the housing 3, which prevents the ingress of liquid. The outlet valve 15 thus prevents the escape of the cut-off air. To ensure that the outlet valve 5 is always operated in the operating state, the drain housing 11 has a separate shut-off air port 18 which opens on the operating side into the outlet valve 15. The outlet valve 15 has a shut-off piston 16 which has an enlarged head side and which presses a compression spring 17 against a stop. By introducing shut-off air via the shut-off air port 18, the shut-off piston is pressed into the outlet hole 14 against the spring force of the compression spring 17 and blocks it.

[0025] When it is desired to end the operating state, the shutoff air is shut off as well, and there is no longer any pressure in the shutoff air port 18. This rest state is shown in Fig. 3. Due to the spring force of the compression spring 17, the shutoff piston 16 is pushed out of the outlet hole 14, and the liquid flowing into the housing 3 is collected in the front cavity 13 forming a liquid reservoir and can flow out of the housing 3 via the outlet hole 14.

[0026] It is therefore possible to propose a steady rest for holding a workpiece, which, as mentioned above, allows for accurate position detection and yet avoids as far as possible damage and injury from penetrating liquids. [Explanation of symbols]

[0027] 1. Vibration Rest 2 Workpiece 3. Housing 4 Housing Cavity 5 3 shutoff air ports 6 Angle lever 7 Operating piston 8 Pressing elements 9 Reflective surface 10 Distance Signal 11 Water drain housing 12 Ultrasonic Sensor 13 Pre-cavity 14 Outflow hole 15 Outlet valve 16 Shut-off piston 17 Compression spring 18 11 shutoff air ports

Claims

1. A brace for holding a workpiece (2) in a machine tool, comprising a substantially vertically movable operating piston (7), with two angle levers (6) positioned on either side of the operating piston (7), the operating piston (7) cooperating with the angle levers (6) via a pressing element (8) inside a housing (3), and the housing (3) being allocated a shut-off air supply passage to prevent liquid ingress, in a brace, A vibration damper characterized in that the operating position of the pressing element (8) is detectable below the lowest position of the pressing element (8) using a distance sensor assigned to the housing (3), and the front cavity (13) of the distance sensor has an outlet hole (14) that can be closed via an air-operated shut-off outlet valve (15) for draining water from the front cavity (13).

2. The damper according to claim 1, characterized in that the distance sensor is oriented parallel to the operating piston (7), and the pressing element (8) has a reflective surface (9) positioned facing the distance sensor for reflecting the distance signal (10) transmitted from the distance sensor.

3. The brace according to claim 1 or 2, characterized in that the outlet valve (15) is assigned a spring-operated shut-off piston (16) that opens the outlet hole (14) in a no-pressure state.

4. The vibration damper according to claim 3, characterized in that a separate shut-off air port (18) is assigned to the shut-off piston (16) on the operating side.

5. The anti-vibration device according to claim 3, characterized in that the shut-off piston (16) is coupled on its operating side to a housing portion to which shut-off air is supplied.

6. The vibration damper according to claim 1 or 2, characterized in that the distance sensor, the pre-cavitation (13), the outlet hole (14), and the outlet valve (15) are housed in a drainage housing (11) that can be detached from the housing (3).

7. The brace according to claim 1 or 2, characterized in that the housing (3) is allocated at least one shut-off air port (5) at at least a locally geodetic low point in the housing cavity (4) formed within the housing (3).

8. The vibration damper according to claim 1 or 2, characterized in that a shut-off air port (5) is allocated to the housing (3) or the drain housing (11) in the area of ​​the distance sensor, preferably in the area of ​​the front cavity (13) of the distance sensor.

9. The vibration damper according to claim 1 or 2, characterized in that the distance sensor is an ultrasonic sensor (12).

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