STEADY REST

Abstract

It is already known to detect the position of a pressure element of a steady rest, by means of which its angle levers are actuated, via a traction cable and its rolling position. Possible penetration of liquid via openings in the housing, present for functioning, is avoided by applying sealing air which generates a positive pressure in the housing. After operation, however, penetrated or penetrating liquid could damage the coiling device of the traction cable and impair the position detection.

The present invention is intended to provide the option to provide a more accurate and simpler detection of the position of the pressure element, and thereby further alleviate the problem of penetrating liquid. This is achieved by use of a distance sensor that detects the position of the pressure element and is drained via a drain hole. During operation the drain hole is closed via a sealing air-actuated discharge valve, so that during operation the sealing air cannot escape through the drain hole, but in the rest state, any liquid that has still penetrated drains off.

Claims

1. A steady rest for holding a workpiece (2) on a machine tool, comprising an essentially perpendicularly disengageable actuating piston (7) which is flanked by an angle lever (6) on both sides, and which within a housing (3) cooperates with the angle levers via a pressure element (8), a sealing air supply for avoiding penetration of liquid being associated with the housing (3), characterized in that a disengaged position of the pressure element (8) is detectable by means of a distance sensor that is associated with the housing (3), below a lowest position of the pressure element (8), and a run-up cavity (13) of the distance sensor for draining the distance sensor via a drain hole (14) that is closeable via a sealing air-actuated discharge valve (15).

2. The steady rest according to claim 1, characterized in that the distance sensor is oriented in parallel to the actuating piston (7), and the pressure element (8) has a reflective surface (9), opposite from the distance sensor, for reflecting a distance signal (10) emitted from the distance sensor.

3. The steady rest according to claim 1, characterized in that a spring-actuated blocking piston (16), which in an unpressurized state opens up the drain hole (14), is associated with the discharge valve (15).

4. The steady rest according to claim 3, characterized in that a separate sealing air connection (18) is associated with the blocking piston (16) on an actuation side.

5. The steady rest according to claim 3, characterized in that the blocking piston (16) is connected on its actuation side to a housing part that is acted on by sealing air.

6. The steady rest according to claim 1, characterized in that the distance sensor, the run-up cavity (13), the drain hole (14), and the discharge valve (15) are accommodated in a drainage housing (11) that is detachable from the housing (3).

7. The steady rest according to claim 1, characterized in that at least one sealing air connection (5) at one at least local geodetic low point of a housing cavity (4) formed in the housing (3) is associated with the housing (3).

8. The steady rest according to claim 1, characterized in that a sealing air connection (5) in the region of the distance sensor, preferably in the region of the run-up cavity (13) of the distance sensor, is associated with the housing (3) or the drainage housing (11).

9. The steady rest according to claim 1, characterized in that the distance sensor is an ultrasonic sensor (12).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention described above is explained in greater detail below with reference to one exemplary embodiment.

[0021] In the figures:

[0022] FIG. 1 shows a steady rest for holding workpieces, with an adjoining drainage housing in a lateral cross-sectional illustration,

[0023] FIG. 2 shows the drainage housing as a detail of the steady rest illustrated in FIG. 1, in an operating state with the discharge valve closed, and

[0024] FIG. 3 shows the drainage housing according to FIG. 2 in an alternative rest state with the discharge valve open.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] FIG. 1 shows a steady rest 1 in which an actuating piston 7 is provided in order to actuate two laterally flanking angle levers 6 via a pressure element 8. The steady rest 1 is in a closed clamped state in which a workpiece 2 is fixed between the holding surfaces, formed by a holding element of the actuating piston 7, and the angle levers 6. To allow the clamping position of the steady rest 1 to be detected as a signal for a tool control, an ultrasonic sensor 12 is provided as a distance sensor, which detects a distance from a reflective surface 9 and thus allows a conclusion to be drawn concerning the position and the clamped state of the pressure element 8. After the pressure element 7 actuates the angle levers 6, the overall clamped state of the steady rest 1 may be deduced.

[0026] If the workpiece 2 is now machined in this position, liquid, for example from the use of cooling lubricant, may enter into the housing 3 which encloses the pressure element 8 as well as the lower areas of the angle levers 6 and the actuating piston 7. Since the ultrasonic sensor must be situated below the lowest deflection of the pressure element 8 in order to be able to detect any possible position of the pressure element 8, the penetrating liquid may collect in a run-up cavity 13 upstream from the ultrasonic sensor 12, and may thus skew the measured values of the ultrasonic sensor 12. Therefore, sealing air is introduced via a sealing air connection 5 into a housing cavity 4 that is formed by the housing 3, so that a positive pressure results in the housing 3. The penetration of liquid, at least during operation, may thus be largely, if not absolutely completely, avoided.

[0027] In order to also remove liquid that still penetrates into the housing after the sealing air is switched off, a drainage housing 11, which in FIG. 2 is illustrated as an enlarged detail from FIG. 1, is mounted at the lowest point. The drainage housing opens into the housing 3 via a run-up cavity 13. The ultrasonic sensor 12 sends its distance signals 10 through the run-up cavity 13, and the reflections of the distance signals are intercepted by the ultrasonic sensor 12; via the time offset of the reflection it is possible to deduce the distance from the reflective surface 9 of the pressure element 8. A drain hole 14 with a downward slope extends from the run-up cavity 13 to the outside, the drain hole 14 being closed by a discharge valve 15. This represents the operating state in which, by introducing sealing air, a positive pressure between 0.5 and 1.0 bar is generated in the housing 3 and the penetration of liquid is thus avoided.

[0028] The discharge valve 15 thus prevents the sealing air from escaping. To ensure that the discharge valve 5 is always actuated in the operating state, the drainage housing 11 has a separate sealing air connection 18 that opens into the discharge valve 15 on the actuation side. The discharge valve 15 includes a blocking piston 16 which has a widening on the head side and which thus presses a compression spring 17 against a stop. Due to the introduction of the sealing air via the sealing air connection 18, the blocking piston is pushed into the drain hole 14, against the elastic force of the compression spring 17, and blocks the drain hole.

[0029] If a departure is to be made from the operating state, the sealing air is likewise discontinued, and pressure is no longer present at the sealing air connection 18. This rest state is shown in FIG. 3. Due to the elastic force of the compression spring 17, the blocking piston 16 is pressed out from the drain hole 14, and liquid entering the housing 3 may collect in the run-up cavity 13 which forms a sump, and may drain from the housing 3 via the drain hole 14.

[0030] The above discussion thus proposes a steady rest for holding a workpiece, which allows precise position detection but avoids damage and impairment from penetrating liquid to the greatest extent possible.

LIST OF REFERENCE NUMBERS

[0031] 1 steady rest [0032] 2 workpiece [0033] 3 housing [0034] 4 housing cavity [0035] 5 sealing air connection of 3 [0036] 6 angle lever [0037] 7 actuating piston [0038] 8 pressure element [0039] 9 reflective surface [0040] 10 distance signal [0041] 11 drainage housing [0042] 12 ultrasonic sensor [0043] 13 run-up cavity [0044] 14 drain hole [0045] 15 discharge valve [0046] 16 blocking piston [0047] 17 compression spring [0048] 18 sealing air connection of 11