Measuring apparatus

• US 20020189123A1
• Filed: 06/12/2002
• Published: 12/19/2002
• Est. Priority Date: 06/13/2001
• Status: Active Grant

• Current Assignee: Smw-Autoblok Spannsysteme GmbH
• Original Assignee: Smw-Autoblok Spannsysteme GmbH
• Inventors: Bercher, Heiuvich, Denzel, Johannes Markus
• Granted Patent: US 6,729,036 B2
• Time in Patent Office: Days
• US Class Current: 33/706
• CPC Class Codes: F15B 15/2846 using detection of markings, e.g. markings on the piston rod
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence
• CPC Class Codes: G01D 5/202 by movable a non-ferromagnetic conductive element G01D5/2033 takes precedence
• CPC Class Codes: Y10S 33/15 Piston position indicator

Abstract

In a measuring apparatus (1) for contactlessly determining the position of two components (11 and 12 respectively) which are displaceable relative to each other and which are in the form of a measurement value sender (11) and a sensor (21) co-operating therewith, the measurement value sender (11) is in the form of a switching ring comprising a metallic material and connected to the displaceable component, and the sensor (21) comprises a plurality of inductive measuring heads which are arranged over the displacement range of the switching ring and which produce an electromagnetic measuring field composed of individual fields. The measuring heads are also connected to a computing unit (25) in which there is stored in a memory the signal configuration ascertained upon calibration of the measuring apparatus (1); the position of the displaceable component can be determined after a displacement movement of the switching ring (12), by comparison of the signals produced, with the stored signal configuration.

This design configuration provides that incorrect measurements are reliably avoided and that a magnetic and a mechanical shock do not have to be tolerated as the measuring apparatus (1) is operational without magnets.

Claims

1. A measuring apparatus (1) for contactlessly determining the position of two components (11 and 21) which are displaceable relative to each other with a translatory movement, in particular for determining the position of a displacement piston (6) which is fitted in a cylinder (5) and which is drivingly connected to clamping jaws (3) of a power-operated chuck (2), wherein the one component is in the form of a measurement value sender (11) and the other component is in the form of a sensor (21) co-operating therewith, the sensor (21) comprises a plurality of inductive measuring heads (22, 22′

, 22″

, 22″

′

. . . ) arranged over the displacement range (s) of the measurement value sender (11), the measuring heads (22, 22′

, 22″

, 22″

′

. . . ) are connected to a computing unit (25) which has an evaluation circuit and in which there is stored in a memory the signal configuration (26) of the individual measuring heads (22, 22′

, 22″

, 22″

′

. . . ), which is ascertained upon calibration of the measuring apparatus (1) in dependence on the position of the measurement value sender (11), and the position of the displaceable component (11) can be determined after an axial displacement movement of the measurement value sender (11) by comparison of the signals respectively produced thereby in the measuring field (24) with the stored signal configuration (26), characterised in that the measurement value sender (11) 1st in the form of a switching ring (12) and comprises a metallic, preferably ferromagnetic material, and the switching ring (12) is provided on the face which is towards the sensor (21, 22, 22′

, 22″

, 22″

′

. . . ) with a profiling (13) formed by at least one recess (14) provided therein.

2. A measuring apparatus as set forth in claim 1 characterised in that the flanks (15, 15′

, 15″

, 15″

′

) of the recesses (14, 14′

) are perpendicular to the axis or are arranged extending inclinedly in a trapezoidal shape inwardly or outwardly relative to the face of the switching ring (12) or are of a convexly or concavely curved configuration.

3. A measuring apparatus as set forth in claim 1 or claim 2 characterised in that two recesses (14, 14′

) which are arranged at a lateral spacing relative to each other are provided in the face of the switching ring (12).

4. A measuring apparatus as set forth in claim 2 or claim 3 characterised in that in the case of a switching ring (12) with recesses (14) which are provided in the face of the switching ring perpendicularly to the axis in relation to the face thereof the recesses (14) and the projections (16) formed thereby are of equal width.

5. A measuring apparatus as set forth in claim 4 characterised in that the lateral spacing (a) of the measuring heads (22, 22′

, 22″

, 22″

′

. . . ) is different from the lateral spacing (b) of two flanks (15), which are directed in the same direction, of two projections (16).

6. A measuring apparatus as set forth in claim 5 characterised in that the spacing (a) of the measuring heads (22, 22′

, 22″

, 22″

′

. . . ) is in a ratio to the spacing (b) of the flanks (15) of three to four.

7. A measuring apparatus as set forth in one or more of claims 1 through 6 characterised in that the measuring heads (22, 22′

, 22″

, 22″

′

. . . ) are arranged equidistantly, preferably in a line, over the displacement range (s) of the switching ring (12).

8. A measuring apparatus as set forth in one or more of claims 1 through 7 characterised in that the measuring heads (22, 22′

, 22″

, 22″

′

. . . ) are respectively formed from a ferrite shell core and a coil pack.

9. A measuring apparatus as set forth in one or more of claims 1 through 8 characterised in that the measuring heads (22, 22′

, 22″

, 22″

′

. . . ) produce an electromagnetic field (24) composed of individual fields (23, 23′

, 23″

, 23″

′

. . . ).