Keypad unit and holder for a keypad unit as well as arrangement

Abstract

A sensing unit (27) for a measuring instrument (20) configured to detect a measured value at a measuring point on an object surface (21) by contact or without contact, wherein the sensing unit (27) comprises: - a carrier (28), - a sensing element (29) arranged on the carrier (28) configured to probe the object surface (21) by contact or without contact, - a fastening device (31) on the carrier (28) configured to be mechanically connected to a holder (26) of the measuring instrument (20), wherein the fastening device (31) comprises a contact unit (32) defining a first longitudinal axis (L1), having a contact surface (34) defining a conical surface around the first longitudinal axis (L1) and being configured to bear against a counter-contact unit (51) of the holder (26) of the measuring instrument (20) in a contact position (P).such that a rotational degree of freedom remains in a circumferential direction (U) about the first longitudinal axis (L1) between the fastening device (31) and the holder (26), and wherein the fastening device (31) has at least one fastening magnet (40, 41, 42) which is configured to cooperate with each of a holder magnet (55, 56, 57) of the holder (26) in the mounting position (P), such that a magnetic axial force (FA) parallel to the first longitudinal axis (L1) is generated between the fastening device (31) and the holder (26), and that a magnetic circumferential force (FU) in a circumferential direction (U) about the first longitudinal axis (L1) is generated between the fastening device (31) and the holder (26) until a predetermined target rotational position (R) about the first longitudinal axis (L1) between the fastening device (31) and the holder (26) is reached, wherein the fastening device (31) has a stop surface (43) exhibitswhich in the intended rotational position (R) rests against a counter-stop surface (60) of the holder (26) such that an offset exists between the magnetic axes (B1, B2, B3) of the fastening magnets (40, 41, 42) and the magnetic axes (H1, H2, H3) of the holder magnets (55, 56, 57), so that a remaining magnetic circumferential force (FU) pushes the stop surface (43) against the counter-stop surface (60).

Description

The invention relates to a probe unit and a holder for a probe unit. The holder for the probe unit can be part of a measuring device, for example. A suitable probe unit can be selected depending on the measurement task and arranged on the holder. The sensing unit is, for example, a sensing arm which is configured for touching tactile sensing and / or for touching an object in a contactless manner and for this purpose carries a tactile sensing element or a touch element detecting in a contactless manner at its end. The measuring device can be, for example, a touch-sensitive device. The invention also relates to an arrangement comprising a probe unit and a holder.A chromatic range finding system according to DE 10 2021 109 449 A1 has an optical pen with a quick-change holder. An optical element can be exchanged by means of the quick-change holder. For this purpose, the quick-change holder on the optical pin has a first mating half and the optical element has a matching second mating half in the form of a front plate, so that the two mating halves form an interface for releasable connection. The holding force for arranging the optical element on the optical pin can be generated by means of permanent magnets, which can be arranged in one or both mating halves. The relative rotational position of this magnetic interface is predetermined by protruding balls in the first mating half and associated V-shaped grooves in the second mating half.JP 3141561 U discloses a roughness meter configured to automatically exchange a roughness gauge. A connection is provided on a probe holder, into which connection the roughness measuring probe can be releasably arranged with an associated connecting device. The holding force can be generated magnetically. The rotational position can be clearly defined via a fitting hole at the edge of the connection and a fitting pin at the edge of the connecting device. The connection can only be produced in the predetermined rotational position.Womnniak, Adam: "Study of the reproducibility of the magnetic joint in the samples used in coordinated measuring machines", The International Journal of Advance Manufacturing Technology 47.9 (2010), pages 1209-1216, deals with the repeatable accuracy of the relative position of probes in coordinate measuring machines, in which the connection between the probe and a holder of the coordinate measuring machine is produced magnetically. The relative rotational position of this magnetic interface is predefined by protruding balls on the probe on the one hand and associated recesses on the holder on the other hand.DE 10 2017 012 202 B4 describes a measuring arm and a measuring arm receiving device of a measuring system. The measuring arm receiving device has a receiving body with a plurality of bearing points, on which the measuring arm rests in each case when the connection is produced. The holding force between the measuring arm and the measuring arm receiving device is generated by a plurality of magnet pairs, wherein one magnet of one magnet pair is arranged on the measuring arm and the other magnet is arranged on the measuring arm receiving device or the receiving body. The receiving body is substantially cuboidal and the measuring arm has an interface, with a cutout adapted to the shape of the receiving body.DE 10 2018 119 697 A1 discloses a measuring device with an optical measuring arrangement. The measuring arrangement has an optical system with several parts which can be connected to one another via a positioning arrangement. For this purpose, the positioning arrangement has three rotationally symmetrical bodies and three corresponding receptacles in order to define the correct position between the two parts of the optical unit. The holding force between the two parts can be generated by magnets.DE 11 2012 005 779 B4 relates to a coordinate measuring machine, in particular a so-called laser tracker. The laser tracker may direct a laser beam to a retroreflector. In one embodiment, the retroreflector has latching elements which can be inserted into fitting elements of a probe head in order to define the relative position. The holding force can be generated magnetically.EP 2 515 069 B1 describes a sensing arm with a sensing arm interface and a holder with an interface matching the sensing arm interface. Balls of a sensing arm interface, which engage in depressions between cylinders on the holder, ensure exact definition of the relative position when the connection is produced. The holding force between the sensing arm and the holder can be applied magnetically. A sensing arm and a holder for the sensing arm with a similar interface is described in DE 10 2017 106 741 B4.DE 10 2019 218 705 A1 discloses a fastening device for fastening a component to an optical device, for example for fastening an objective to a microscope. On the device and on the component, a magnetic holding arrangement with a plurality of magnets is provided. To generate a magnetic holding force when the connection is produced, the magnets form pairs in each case. In making the connection, the components may be rotated in the direction of rotation to bring the two magnets of each pair into agreement.EP 2 847 540 B1 discloses an illumination module and an optical sensor of a coordinate measuring machine. The illumination module and the sensor are mounted on each other via a three-point bearing and held on each other via a magnetic holding force. The magnet can be a permanent magnet or a switchable electromagnet.DE 10 2018 133 220 A1 and DE 10 2005 007 003 B4 each describe an interface for arranging a sensing element on a carrier of the sensing unit, in particular a sensing arm.Sensing units with a replaceable sensing element are known and are offered, for example, by the companies Optacom GmbH & Co. KG or Trusworx GmbH & Co. KG.The sensing element for sensing the measurement location on an object surface must be suitable for the measurement task. A tactile sensing element is also subject to some wear. It may therefore be desirable to replace the sensing element or the sensing unit depending on the measurement task or in the event of wear occurring. The exchange of the sensing element or the sensing unit is cumbersome in many known systems. In the installed state in the measuring device, the probe unit is not always easily accessible from all sides without problems. In addition, in some of the known systems, the exchange of the probe unit or probe element leads to the introduction of forces into the measuring device, as a result of which in turn very delicate components of the measuring device, which serve for generating the measuring force or for measuring value detection, are subjected to increased, in particular mechanical, stress and could be damaged.It is therefore an object of the present invention to provide a probe unit and a holder of a measuring device which can be easily replaced on the holder, in particular without tools.This object is achieved by a sensing unit having the features of claim 1, a holder having the features of claim 8 and an arrangement having the features of claim 13.The probe unit according to the invention for a measuring device can be, for example, a probe arm or a probe arm section or can have another substantially rod- or tubular shape. The measuring device is configured to record a measured value at a measurement point of an object surface with the aid of the probe unit. The sensing unit thus serves to sense the object surface at the measurement location. The sensing unit can operate in a touching or contactless manner, for example, in a tactile or optical manner.The sensing unit has a carrier. The carrier can be rod-shaped or tubular, for example. A sensing element is arranged on the carrier. The sensing element is configured to lie touching the measurement location on the object surface or to be directed contactless to the measurement location on the object surface. For example, the sensing element can emit light or another electromagnetic wave onto the measurement point, which is reflected there and received again by the sensing element.On the carrier of the sensing unit, a fastening device is also provided. The fastening device can be a monolithic component of the carrier or can be attached to the carrier. The fastening device is configured to detachably mechanically connect the probe unit to a holder of the measuring device. In addition to the mechanical connection, a signal transmission connection can optionally also be produced, for example an electrical connection and / or an optical connection.In particular, the fastening device is designed such that it can be connected to the holder of the measuring device without the use of a tool and can be separated from the holder of the measuring device without the use of a tool. Preferably, the connection between the fastening device and the holder is free of a screw connection and / or a latching connection.The fastening device has an abutment unit. The contact unit has a contact surface. The contact unit and in particular the contact surface defines a first longitudinal axis.In one embodiment, the carrier extends along the first longitudinal axis, wherein the first longitudinal axis can be a central axis or central axis of the carrier, for example a rod-shaped or tubular carrier.The contact unit is configured to assume a contact position in which it bears against a counter-contact unit of the holder of the measuring device. In the bearing position, a rotational degree of freedom remains in a circumferential direction about the first longitudinal axis between the fastening device and the holder or between the bearing unit and the counter bearing unit. The sensing unit is thus rotatable about the first longitudinal axis relative to the holder.Preferably, in the bearing position, up to three translatory degrees of freedom and up to two rotatory degrees of freedom are eliminated by the bearing unit and the counter bearing unit, so that in particular only the rotatory degree of freedom about the first longitudinal axis remains when the bearing unit is in the bearing position with the counter bearing unit.The fastening device has at least one fastening magnet, which preferably has at least one magnetic pole on the end face. It is advantageous if a plurality of fastening magnets are present. The at least one fastening magnet is configured to cooperate with at least one holding magnet of the holding device, at least in the contact position and in the vicinity of the contact position. The at least one holder magnet preferably has at least one magnetic pole on the end face of the holder. By the cooperation of the magnets, a magnetic axial force parallel to the first longitudinal axis and additionally a magnetic circumferential force in a circumferential direction about the first longitudinal axis are generated between the fastening device and the holder. The circumferential magnetic force urges the fastener to a desired circumferential rotational position about the first longitudinal axis relative to the bracket. The magnetic circumferential force is dimensioned outside the desired rotational position in such a way that the frictional and sliding friction between the contact unit and the counter-contact unit is overcome, so that the fastening device assumes the desired rotational position relative to the holder in the circumferential direction.The desired rotational position is defined by a stop surface of the fastening device in cooperation with a counter-stop surface of the holder. The stop surface of the fastening device abuts the counterstop surface of the holder when the fastening device assumes the desired rotational position relative to the holder in the circumferential direction about the first longitudinal axis.Thus, the connection between the probe unit and the holder is very easily established by bringing the contact unit into contact with the counter contact unit. The holding force is generated magnetically and holds the sensing unit in contact with the holder in the axial direction parallel to the first longitudinal axis. The abutment position is maintained by the axial magnetic force. In addition, a magnetic circumferential force is provided in order to eliminate the remaining rotational degree of freedom in the circumferential direction and to bring the fastening device into the desired rotational position relative to the holder.This connection can be released again very easily by overcoming the magnetic force. The production and the release of the connection can be carried out without tools.The establishment and the release of the connection can be carried out manually by an operator. In addition, automated establishment and detachment of the connection between the fastening device and the holder is also possible, for example by means of a manipulator, such as a gripping device, a robot, etc. This also allows automatic changing of a probe unit in the holder of the measuring device.It is advantageous if the at least one fastening magnet and / or the at least one holding magnet is a permanent magnet. Preferably, the at least one fastening magnet and / or the at least one holding magnet is exclusively axially magnetized, i.e. its magnet axis preferably extends substantially parallel to the first longitudinal axis. Alternatively, the at least one fastening magnet and / or the at least one holding magnet can be magnetized axially and radially or exclusively radially. In all embodiments, each mounting magnet and / or each mounting magnet may have exactly one or more north poles and south poles.It is advantageous if the abutment unit is present at a tapering end of the carrier. This tapering end of the carrier can be bounded by a virtual frustoconical lateral surface, within which contact with the counter-bearing unit exists in the bearing position, no component of the bearing unit projecting through the virtual frustoconical lateral surface.In a preferred embodiment, the fastening device has a plurality of fastening magnets. The fastening magnets are arranged uniformly distributed in the circumferential direction about the first longitudinal axis. The magnet axes are preferably oriented parallel to one another and parallel to the first longitudinal axis. Alternatively, the magnet axes can also be arranged obliquely inclined to the first longitudinal axis, wherein the magnet axes of the fastening magnets then preferably intersect at a common point on the first longitudinal axis.If a plurality of fastening magnets are present, it may be advantageous to choose the polarity of at least two of the fastening magnets present to be opposite, as seen parallel to the first longitudinal axis. The magnetization direction parallel to the first longitudinal axis of these fastening magnets is therefore opposite or antiparallel. This allows the fixing magnets and the associated holder magnets to repel each other when the fixing device and the holder assume a rotational position in the circumferential direction which is far from the target rotational position and the magnetic axial force causes attraction only when the fixing device and the holder assume a relative position in the circumferential direction which is sufficiently close to the target rotational position. This aspect of the invention can also be realized independently of all other features of the sensing unit.As explained, the contact unit has a contact surface. The contact surface can be contiguous in the circumferential direction. In a preferred embodiment, the contact surface is divided in the circumferential direction into a plurality of surface sections which are separated from one another and are arranged at a distance from one another. The contact surface is rotationally symmetrical about the first longitudinal axis in the circumferential direction and corresponds in particular to a truncated cone lateral surface or at least sections thereof. When the contact surface is divided into surface sections, these are arranged on a common virtual truncated cone lateral surface about the first longitudinal axis and preferably uniformly distributed in the circumferential direction.It is preferred if all surface sections have the same surface area and / or the same shape.In a particularly advantageous embodiment, the optionally present stop surface can be arranged in the circumferential direction between two adjacent surface sections. This configuration results in a particularly compact design of the fastening device.The stop surface can be oriented parallel to the axial direction and / or substantially at right angles to the circumferential direction.The at least one fastening magnet of the fastening device is preferably arranged closer to the first longitudinal axis than the contact unit or the contact surface of the contact unit. The contact surface can thus enclose the fastening magnets in the circumferential direction.The invention also relates to a holder of the measuring device, which is configured for attaching a probe unit to the measuring device. The holder has a holding body on which a counter-contact unit is present. The holding body can be rod-shaped or tubular. The counter-abutment unit defines a second longitudinal axis. The counter-contact unit preferably has a counter-contact surface on a counter-contact body which is continuous in the circumferential direction about the second longitudinal axis and is thus closed in an annular or tubular manner. The counter-contact surface can be, for example, a truncated cone lateral surface.The counter-contact unit is configured to contact a contact unit of a fastening device of a sensing unit when the fastening device is in a contact position relative to the holder. In the contact position, a rotational degree of freedom about the longitudinal axis remains between the fastening device and the holder.The bearing unit and the counter bearing unit are in particular configured such that the first longitudinal axis of the bearing unit and the second longitudinal axis of the counter bearing unit are aligned along a common straight line in the bearing position and thus form a common longitudinal axis.A direction parallel to one of the longitudinal axes is referred to as an axial direction. A direction of rotation about one of the longitudinal axes is referred to as the circumferential direction.The holder has at least one holder magnet, which cooperates with at least one fastening magnet of the fastening device, at least in the contact position or in the vicinity of the contact position. In the bearing position, the cooperation of the at least one holding magnet with the at least one fastening magnet generates a magnetic axial force parallel to the second longitudinal axis and a magnetic circumferential force in the circumferential direction about the second longitudinal axis. The magnetic axial force holds the fastening device in the bearing position on the holder. The magnetic peripheral force allows a frictional force between the bearing unit and the counter bearing unit to be overcome in order to set a setpoint rotational position between the fastening device and the holder.It is preferred that the number of the holding magnets corresponds to the number of the fixing magnets. Each holding magnet forms a magnet pair with a respective associated fastening magnet. The holding magnet and the fastening magnet of a common magnet pair are magnetized in opposite directions to one another, so that the south pole of the holding magnet faces the north pole of the fastening magnet or vice versa.It is preferred if the at least one holding magnet is axially magnetized, i.e. its magnet axis is aligned substantially parallel to the second longitudinal axis. If a plurality of holding magnets are present, they are preferably arranged uniformly distributed in the circumferential direction about the second longitudinal axis. The magnet axes of the support magnets are oriented parallel to each other or alternatively may intersect at a common point on the second longitudinal axis.It is preferred if two of the existing holder magnets are polarized in opposite directions as seen in the axial direction, i.e. have opposite magnetization directions. This aspect of the invention can also be realized independently of all other features of the holder.The counter-contact unit can be formed by a tubular counter-contact body of the holder. The counter-contact surface is preferably located within the tubular counter-contact body. The counter-contact body can be a monolithic component of the holding body.Preferably, the contact unit or the contact surface is made of a material which has a higher elasticity than the material of the counter-contact unit or the counter-contact surface. The contact unit or the contact surface can consist of a plastic. The counter bearing unit or the counter bearing surface can consist of a metallic material, in particular of a steel alloy. This allows production of the contact unit and the counter-contact unit with greater manufacturing tolerances than in the case of a material pairing with materials of the same elasticity.In a modified exemplary embodiment, it is also possible for the bearing unit or the bearing surface, on the one hand, and the counter-bearing unit or the counter-bearing surface, on the other hand, to each consist of the same material, for example of a steel alloy.A further aspect of the present invention relates to an arrangement comprising a sensing unit and a holder. The sensing unit and the holder can preferably be formed according to any of the above embodiments.In this aspect of the arrangement, the sensing unit has a carrier, a sensing element arranged on the carrier and a fastening device present on the carrier. The fastening device is configured to be connected to the holder of the measuring device. The attachment device has an abutment unit defining a first longitudinal axis. In addition, the fastening device has at least one fastening magnet.The holder of the arrangement has a holding body with a counter-abutment unit which defines a second longitudinal axis. The holder also has at least one holder magnet.The at least one mounting magnet and the at least one mounting magnet cooperate. Magnetic repulsion is thereby brought about when the sensing unit and the holder of the arrangement are arranged in a relative rotational position about the first longitudinal axis and the second longitudinal axis, which lies within a first rotational position range. An attractive force is caused between the at least one fastening magnet and the at least one holder magnet when the relative rotational position of the sensing unit and the holder is in a second rotational position range different from the first rotational position range. The second rotational position range corresponds to or contains the desired rotational position of the sensing unit and the holder in the circumferential direction about the longitudinal axes. An attraction is therefore only effected if the relative rotational position between the sensing unit and the holder corresponds sufficiently well to the desired rotational position. This aspect of the invention simplifies the mechanical connection of the probe unit and the holder to one another and prevents misalignment of the probe unit with respect to the holder.In a further independent aspect of this invention, the above-described interface of the probe unit for connection to the holder can also be used as an interface for other bodies, for example a slide with an object arranged thereon, for an object holder (e.g. chuck) for an object to be measured, for an abutment tip or another bearing or support element, by means of which in particular an object to be measured can be supported, etc.On this body there can then be the fastening device which is configured to be mechanically connected to a holder. The attachment means of the body may be according to any of the embodiments explained above in connection with the sensing unit. The holder may be any of the above embodiments.The fastening device has the contact unit which defines the first longitudinal axis. The contact unit is configured to bear against the counter-contact unit of the holder in a contact position, such that a rotational degree of freedom remains in a circumferential direction about the first longitudinal axis between the fastening device and the holder. The fastening device has at least one fastening magnet which is configured to cooperate with a respective holder magnet of the holder in the bearing position, so that a magnetic axial force parallel to the first longitudinal axis is generated between the fastening device and the holder, and that a magnetic circumferential force in a circumferential direction about the first longitudinal axis is generated between the fastening device and the holder until a predefined desired rotational position about the first longitudinal axis is reached between the fastening device and the holder.Advantageous embodiments of the invention are evident from the dependent claims, the description and the drawing. Preferred exemplary embodiments are explained in detail below with reference to the attached drawings. In the drawing, the following are shown: FIG. 1 shows a perspective illustration of an exemplary embodiment of a measuring device, FIG. 2 shows a schematic view of a holder of the measuring device and of a probe unit connected to the holder, FIG. 3 shows a perspective illustration of an exemplary embodiment of a fastening device which is arranged on a holder in an exemplary embodiment, FIG. 4 shows a longitudinal section along a common longitudinal axis through the fastening device and the holder from FIG. 3, FIG. 5 shows a perspective view of an exemplary embodiment of a fastening device, FIG. 6 shows a perspective view of an exemplary embodiment of a holder, FIG. 7 shows a schematic plan view of the fastening device from FIG. 5 viewed in the axial direction parallel to a first longitudinal axis, FIG. 8 shows a schematic plan view of the holder from FIG. 6 viewed in the axial direction parallel to a second longitudinal axis, FIGS. 9-12 each show a schematic basic illustration of the relative arrangement of fastening magnets of the fastening device and holding magnets of the holder in an abutment position between the fastening device and the holder during the production of a desired rotational position in the circumferential direction about the common longitudinal axis, FIG. 13 shows an arrangement of an object carrier with an object, wherein the object carrier is arranged on a holder by means of a fastening device, and FIG. 14 shows an arrangement of a bearing element for an object, wherein the bearing element is arranged on a holder by means of a fastening device.FIG. 1 illustrates an exemplary embodiment of a measuring device 20. The measuring device 20 is configured to acquire or determine a measured value at a measurement point on an object surface 21 of an object 22. For example, a surface contour, a roughness or the like can be determined by means of the measuring device 20.For the measurement value acquisition, the measuring device 20 has a holder 26; the holder 26 serves for the detachable attachment of a probe unit 27. the holder 26 can be mounted, for example, such that it can be pivoted about a pivot axis S. The measuring device 20 can be configured to apply a moment about the pivot axis S to the holder 26 and a sensing unit 27 held therein and / or to detect a deflection of the holder 26 or the sensing unit 27 arranged therein about the pivot axis S and to determine the measured value therefrom. Additionally or alternatively, the holder 26 and the sensing unit 27 arranged therein can be positioned by rotation about the pivot axis S in order to adjust a distance between the sensing unit 27 and the object surface 21.The sensing unit 27 can operate in a touching or tactile manner or also in a contactless manner.The sensing unit 27 has a carrier 28, and the carrier 28 has a sensing element 29 at one end, which is configured in the exemplary embodiment for bearing against the object surface 21. In this embodiment, the sensing unit 27 operates tactilely. The sensing element 29 can have a defined geometry at its end assigned to the object surface 21, for example a tip, a ball or the like.As a modification to this, the sensing element 29 can also operate in contactless fashion and, for example, emit light onto the object surface 21 and receive light reflected from there.The sensing element 29 can optionally be attached to the carrier 28 in an exchangeable manner, for example by means of a force-fit and / or form-fit connection. For example, in one embodiment, a clamping screw 30 may be provided on the carrier 28 to apply a clamping force to the sensing element 29 and hold it on the carrier 28. In other exemplary embodiments, the sensing element 29 can also be non-detachably fastened to the carrier 28, in particular in the case of sensing element 29 having very small dimensions.At an end of the carrier 28 of the sensing unit 27 opposite the sensing element 29, a fastening device 31 is provided. The fastening device 31 is configured to produce a releasable connection with the holder 26. Details of the fastening device 31 are evident in particular from FIGS. 4, 5 and 7.The fastening device 31 has a contact unit 32. The abutment unit 32 defines a first longitudinal axis L 1. In the exemplary embodiment, the contact unit 32 is formed by a contact body 33 which tapers towards its free end. The contact body 33 can be at least partially frustoconical.In the following description, in addition to the first longitudinal axis L 1, a second longitudinal axis L 2 and a common longitudinal axis L are also mentioned. A direction parallel to one of these longitudinal axes is referred to as (respective) axial direction A. A direction of rotation about one of these longitudinal axes is referred to as (respective) circumferential direction U.The contact unit 32 has a contact surface 34, which at least partially encloses the first longitudinal axis L 1 in the circumferential direction U. In the circumferential direction U, the contact surface 34 can be contiguous. In the preferred exemplary embodiment illustrated here, the contact surface 34 is divided into a plurality of separate surface sections 34 awhich are arranged at a distance from one another in the circumferential direction U. Preferably, the surface sections 34 aare identical. In the exemplary embodiment, the surface sections 34 aare each formed by a section or region of a truncated cone lateral surface which extends over a limited angular range in the circumferential direction. This angular range is, for example, smaller than 120° and preferably smaller than 60° or smaller than 30° or smaller than 20°. According to the example, the angular range is less than 10°. The surface sections 34 aare preferably arranged uniformly distributed in the circumferential direction about the first longitudinal axis L 1.Adjacent to the surface sections 34 a, the contact body 33 has recesses or depressions, which in the exemplary embodiment are formed by flattened portions 35 on the contact body 33, compared with a truncated cone whose circumferential surface contains the surface sections 34 a. Between two surface sections 34 aof the contact surface 34 adjacent in the circumferential direction U, one or more such flattened portions 35 can be present. In the exemplary embodiment, each flattened portion is formed by a planar surface which extends in the axial direction A. By means of these flattened portions 35 or recesses, the contact body 33 is reduced in size relative to a frustoconical contact body having a contact surface 34 which is formed by a virtual frustoconical lateral surface. Outside the surface sections 34 aof the contact surface 34, the contact body 33 is at a smaller distance from the first longitudinal axis L 1 than the virtual frustoconical lateral surface 36 at the flattened portions 35 or recesses.In the exemplary embodiment illustrated here, the flattened portions 35 are planar surfaces which extend parallel to the axial direction A.The total surface area of all surface sections 34 atogether is preferably significantly less than the surface area of the virtual truncated cone lateral surface 36.In a modification to the illustrated exemplary embodiment, the contact surface 34 could also be contiguous in the circumferential direction U, for example a surface corresponding to the virtual frustoconical lateral surface 36. By means of the recesses or flattened portions 35 and the reduction of the contact surface 34 to a plurality of surface sections 34 awhich are configured to contact a corresponding counter-contact surface, the frictional and sliding friction between the contact surface 34 and the associated counter-contact surface can be reduced.Preferably, the contact surface 34 has exactly three or at least three separate surface sections 34 a.In a modification to the illustrated exemplary embodiment, the recesses or flattened portions 35 on the contact body 33 could also be designed differently in order to reduce the total surface area of the contact surface 34 or of the surface sections 34 a. In this case, the surface sections 34 acan be completely separated from one another or can be contiguous at least in sections.The fastening device also has at least one and preferably a plurality of fastening magnets, for example a first fastening magnet 40, a second fastening magnet 41 and a third fastening magnet 42. the first fastening magnet 40 has a first magnet axis B 1, the second fastening magnet 41 has a second magnet axis B 2 and the third fastening magnet 42 has a third magnet axis B 3 (FIG. 7 ). In the exemplary embodiment, the magnetic axes B 1, B 2, B 3 are oriented parallel to the axial direction A. Alternatively, the magnetic axes B 1, B 2, B 3 could intersect at a common point on the first longitudinal axis L 1.The fastening magnets 40, 41, 42 are magnetized in the axial direction A according to the example, so that their magnetic field lines enter or exit at the axial end surfaces in the axial direction A. The north pole and the south pole of each fastening magnet 40, 41, 42 are adjacent to one another in the direction of the respective magnet axis B 1, B 2, B 3.In the exemplary embodiment, two of the fastening magnets present have opposite magnetizations or magnetic polarizations, so that their magnetization directions are antiparallel to one another. In the embodiment, the second fixing magnet 41 has an opposite magnetic polarization as compared to the first fixing magnet 40 and the third fixing magnet 42. The mounting magnets with identical symbols for the magnet axes have the same direction of magnetization.The fastening magnets 40, 41, 42 are arranged, according to the example, within the contact body 33. They are arranged closer to the first longitudinal axis L 1 than the surface sections 34 aof the contact surface 34.In the exemplary embodiment described here, the fastening device 31 also has a stop surface 43. It can be present between two surface sections 34 aadjacent in the circumferential direction on the contact body 33. The stop surface 43 can be formed by a planar surface. In the exemplary embodiment, the stop surface 43 is oriented substantially at right angles to the circumferential direction U. As can be seen in particular in FIG. 7, the stop surface 43 is oriented parallel to the axial direction A in the illustrated exemplary embodiment.The end face 44 of the contact body 33 is oriented at right angles to the first longitudinal axis L 1 in the exemplary embodiment. The fastening magnets 40, 41, 42 are offset with respect to the end face 44 and in particular do not project beyond the end face 44.The configuration of the holder 26 is evident in particular from FIGS. 4, 6 and 8. The holder 26 defines a second longitudinal axis L 2 which, when the connection to the fastening device 31 is produced, coincides with the first longitudinal axis L 1 defined by the fastening device 31 and thus forms a common longitudinal axis L (FIGS. 2-4 ).The holder 26 has a holding body 50 with a counter-contact unit 51. The counter-abutment body 52 can be a monolithic component of the holding body 50. For example, one end of the support body 50 may form the counter abutment body 52.The counter-abutment body 52 can be a tubular body contiguous in the circumferential direction U and is preferably not slotted or otherwise interrupted. The counter-abutment body 52 is designed as a hollow body and encloses the second longitudinal axis L 2 coaxially. On its inner side facing the second longitudinal axis L 2, the counter-contact body 52 has a counter-contact surface 53.Half the opening angle of the virtual frustoconical lateral surface 36 and the frustoconical lateral surface of the counter-bearing surface 53 relative to the second longitudinal axis L 2 is preferably of the same size and in particular less than 10° or less than 5°. The frustoconical lateral surface of the counter-bearing surface 53 and the virtual frustoconical lateral surface 36 of the fastening device 31 are identical according to the example.In an abutment position P of the fastening device 31, the surface sections 34 aof the abutment surface 34 each bear flat against the counter abutment surface 53 or at least linearly in a radial plane having the first longitudinal axis L 1. In the bearing position P, a rotational degree of freedom remains in the circumferential direction U about the common longitudinal axis L. This rotational degree of freedom is given in the exemplary embodiment by the bearing surface 34 or its surface sections 34 aand the counter bearing surface 53 being rotationally symmetrical to the second longitudinal axis L 2 and the surface sections 34 abeing arranged rotationally symmetrically to the first longitudinal axis L 1 (the surface sections 34 aare arranged within the virtual frustoconical lateral surface 36 about the first longitudinal axis L 1).The other rotational degrees of freedom about the axes at right angles to the common longitudinal axis L and the translational degrees of freedom in the axial direction A and at right angles to the common longitudinal axis L are eliminated in the bearing position P by the bearing unit 32 or the counter bearing unit 51.The holder 26 also has at least one holder magnet, wherein the number of holder magnets preferably corresponds to the number of fastening magnets of the fastening device 31. Thus, in the preferred embodiment illustrated here, the holder 26 has a first holder magnet 55, a second holder magnet 56 and a third holder magnet 57. Analogously to the fastening magnets 40, 41, 42, the holder magnets 55, 56, 57 are magnetized in the axial direction A, so that the north pole and the south pole of each holder magnet 55, 56, 57 are arranged next to one another in the axial direction A. The first support magnet 55 has a first magnet axis H 1, the second support magnet 56 has a second magnet axis H 2, and the third support magnet 57 has a third magnet axis H 3 (FIG. 8 ). The magnetic axes H 1, H 2, H 3 are aligned in the axial direction A in the exemplary embodiment. Alternatively, the magnet axes H 1, H 2, H 3 of the holding magnets 55, 56, 57 could intersect at a common point on the second longitudinal axis L 2.The counter-contact body 52, which is designed as a hollow body or tube according to the example, surrounds an inner region 58. Preferably, the holding magnets 55, 56, 57 do not project, or only insignificantly project, into the inner region 58. In the axial direction A, the inner region 58 is bounded by an axial surface 59 on the counter-contact body 52. In the exemplary embodiment, the axial surface 59 is oriented at right angles to the second longitudinal axis L 2. The holding magnets 55, 56, 57 are preferably offset with respect to the axial surface 59 and do not project beyond the axial surface 59 into the inner region 58.Each holding magnet 55, 56, 57 forms a magnet pair with an associated fastening magnet 40, 41, 42. When the fastening device 31 and the holder 26 are connected, these magnet pairs generate a magnetic axial force, whereby fastening magnets 40, 41, 42 and the holder magnets 55, 56, 57 attract each other in the axial direction A. As a result, the fastening device 31 is held on the holder 26 in the bearing position P and the surface sections 34 aof the bearing surface 34 remain in contact with the counter-bearing surface 53.In the circumferential direction U, in the bearing position P, a desired rotational position R is defined by the stop surface 43 of the fastening device 31 and a counterstop surface 60 of the holder 26. In the exemplary embodiment, the counterstop surface 60 is arranged on a counterstop 61. The counterstop 61 is arranged in the inner region 58. In the exemplary embodiment, the counterstop 61 is pin-shaped, for example cylindrical. The counterstop surface 60 is formed by the outer surface or lateral surface of the counterstop 61 or at least a portion thereof.The schematic schematic diagrams of FIGS. 9-11 explain the establishment of the detachable connection between the fastening device 31 and the holder 26.The sensing unit 27 can be held in the hand on the carrier 28, for example, and can be aligned with its first longitudinal axis L 1 approximately in alignment with the second longitudinal axis L 2 of the holder 26. The fastening device 31 is then brought closer to the holder 26 and the contact body 32 is introduced into the inner region 58.Assuming that the current rotational position between the fastening device 31 and the holder 26 deviates significantly (for example by 120° or more) from the desired rotational position R (first rotational position range), the fastening magnets and the holder magnets are at least partially offset, so that a metrologically correct and / or stable connection cannot be easily established. Only when the rotational position between the fastening device 31 and the holder 26 substantially corresponds (second rotational position range) is an attracting magnetic axial force FA generated by all magnets 40, 41, 42, 55, 56, 57, so that the fastening device assumes the contact position P in which the surface sections 34 aof the contact surface 34 contact the counter-contact surface 53. This aspect of the invention can also be realized independently of all other features of the sensing unit 27 and the holder 26, in particular independently of whether a circumferential force FU is also generated by the existing fastening magnets 40, 41, 42 and / or holder magnets 55, 56, 57.In the exemplary embodiment, the contact position P is defined exclusively by the surface sections 34 aand the counter-contact surface 53. In particular, the fastening magnets 40, 41, 42 are not in direct contact with the holding magnets 55, 56, 57 and in the exemplary embodiment, the end face 44 and the axial face 59 are also arranged at a distance from one another. In the bearing position P outside the desired rotational position R, contact between the fastening device 31 and the holder 26 takes place exclusively via the surface sections 34 aand the counter bearing surface 53.As illustrated in FIG. 9, the magnet axes B 1, B 2, B 3 of the fixing magnets 40, 41, 42 are arranged offset in the circumferential direction U from the magnet axes H 1, H 2, H 3 of the holding magnets 55, 56, 57, so that in addition to the axial magnetic force FA, a circumferential magnetic force FUor a magnetic torque is generated in the circumferential direction U. The magnetic torque or the magnetic circumferential force FUis directed such that the stop surface 43 and the counterstop surface 60 are urged toward one another, so that the fastening device 31 is urged relative to the holder 26 in the direction of its desired rotational position R.In a modification to the illustrated exemplary embodiment, it is also sufficient if only one or at least not all of the magnet axes B 1, B 2, B 3 of the fastening magnets 40, 41, 42 is or are arranged offset in the circumferential direction U with respect to the respectively associated magnet axis H 1, H 2, H 3 of the associated mounting magnet 55, 56, 57 in order to generate the circumferential force FU the magnetic torque in the circumferential direction U.Due to the material pairing and the small surface or linear contact between the surface sections 34 aand the counter bearing surface 53, the static friction and the sliding friction outside the desired rotational position R are sufficiently small so that due to the magnetic circumferential force FU a rotational movement is caused between the fastening device 31 and the holder 26 into the desired rotational position R. As a result, the stop surface 43 and the counterstop surface 60 approach each other. With this approach, the magnetic axes B 1, B 2, B 3 of the fastening magnets 40, 41, 42 also approach the respectively associated magnet axis H 1, H 2, H 3 of the associated holding magnet 55, 56, 57, whereby the amount of the magnetic torque or the magnetic circumferential force FU decreases (FIG. 10 ). When the desired rotational position R is finally reached, the stop surface 43 abuts against the counterstop surface 60 (FIGS. 11 and 12 ).In the desired rotational position R, there is still an offset between the magnet axes B 1, B 2, B 3 of the fastening magnets 40, 41, 42 and the magnet axes H 1, H 2, H 3 of the holding magnets 55, 56, 57, so that even when the desired rotational position R is reached, a magnetic torque or a magnetic circumferential force FU is maintained and the stop surface 43 pushes against the counterstop surface 60 (FIG. 11 ). In a variation not according to the invention, the circumferential magnetic force FU could also be equal to zero when the desired rotational position R is reached. In this case, the stopper surface 43 and the counter stopper surface 60 may be omitted, and the target rotational position R may be set by the magnet axes of the fixing magnets 40, 41, 42 and the holding magnets 55, 56, 57, as schematically illustrated in FIG. 12.To release the produced connection, a relative rotation can be carried out between the fastening device 31 and the holder 26, so that the stop surface 43 moves away from the counterstop surface 60. If a sufficiently large relative rotation takes place, the fastening magnets 40, 41, 42 and the holding magnets 55, 56, 57 repel in the axial direction A, since not all fastening magnets 40, 41, 42 and not all holding magnets 55, 56, 57 have the same magnetic polarity. As far as two north poles and / or two south poles approach one another or are opposite one another in the axial direction A as a result of the relative rotation, repulsion takes place between the fastening device 31 and the holder 26 or the remaining attractive force in the axial direction A is reduced in such a way that the sensing unit 27 can be removed from the holder 26 by being pulled out of the inner region 58 in the axial direction.In this way, a manual or automated changing of the sensing unit 27 can take place very easily. The forces acting on the holder 26 and therefore on the measuring device 20 are very low, so that excessive loading of the mechanical and / or electrical and / or electronic and / or optical components of the measuring device 20 is avoided. The sensing unit 27 can be inserted and detached without using a tool.The above-described interface between the probe unit 27 and the holder 26 can be used not only for a probe unit but also for other bodies, for example for object holders such as e.g. object slides, chuck, bearing or supporting elements, etc. Examples thereof are schematically illustrated in FIGS. 13 and 14. The holder 26 can also be configured in the exemplary embodiments according to FIGS. 13 and 14, as has been explained above. Instead of the carrier 28, a holding body 65 can be arranged on the holder 26. For this purpose, the holding body 65 has the fastening device 31, which corresponds to one of the exemplary embodiments described above.In the embodiment according to FIG. 13, an object 66 is connected to the object holder. The object 66 may be, for example, an object 66 to be measured. The object 66 can be a lens, for example. The object 66 can be arranged detachably on the holding body 65 by suitable means or devices. The holding body 65 can have, for example, clamping means in order to hold the object 66 in a force-fit and / or form-fit manner.FIG. 14 illustrates a further possible embodiment in which a bearing or support element 67 is arranged on the holding body 65. The bearing or support element is designed as a bearing tip in the exemplary embodiment. The support member 67 may be used to support an object 66 to be measured or a support body 65. In the exemplary embodiment shown, a conical depression designed in accordance with the bearing tip can be present on the object 66 or on the holding body 65.In the embodiment according to FIG. 13, the common longitudinal axis L is identical to an axis of symmetry of the object 66 to be measured. In the embodiment shown in FIG. 14, the common longitudinal axis L is the longitudinal central axis or axis of symmetry of the bearing or support element 67.If a torque in the circumferential direction U can act on the object 66 or the bearing or support element 67, it is advantageous if only a direction of rotation in the circumferential direction U is permitted in which the torque acts. This direction of rotation should be oriented in such a way that the stop surface 43 of the fastening device 31 is forced against the counterstop surface 60 of the holder 26. Additionally or alternatively, other means may be provided to support circumferential torque in one or both turning centers. For example, when the desired rotational position R is reached, a locking can take place between the holding body 65 and the holder 26, so that the locking supports torques in one rotational direction or in both rotational centers in the circumferential direction U. To release the holding body 65, the locking can be unlocked.The invention relates to a probe unit 27 and a holder 26 of a measuring device 20, which can be connected to one another and separated from one another in a detachable manner in particular without tools. For this purpose, the sensing unit 27 has a fastening device 31 with a contact surface 34 and the holder has a counter-contact surface 53 assigned to the contact surface 34. the contact surface 34 can be divided into a plurality of surface sections 34 aseparated from one another, which each bear linearly or flatly against the assigned counter-contact surface when the fastening device 31 assumes a contact position P. The holding force is generated by at least one fastening magnet 40, 41, 42 of the fastening device 31 and / or at least one holding magnet 55, 56, 57 of the holder 26. In this case, a magnetic axial force FAin an axial direction A and a magnetic circumferential force FUin the circumferential direction U about the axial direction A are generated, so that the fastening device 31 and the holder 26 are urged relative to one another in the circumferential direction U in the direction of a desired desired rotational position R.List of reference numbers:20 Measuring device 21 Object surface 22 Object 26 Holder 27 Sensing unit 28 Carrier 29 Sensing element 30 Clamping screw 31 Fastening device 32 Contact unit 33 Contact body 34 Contact surface 34 a Flächen portion of the contact surface 35 Flattened portions 36 Virtual frustoconical lateral surface 40 First fastening magnet 41 Second fastening magnet 42 Third fastening magnet 43 Stop surface 44 End surface of the contact body 50 Holding body 51 Counter-contact unit 52 Counter-contact body 53 Counter-contact surface 54 Depression 55 First holding magnet 56 Second holding magnet 57 Third holding magnet 58 Inner region 59 Axial surface 60 Counter-stop surface 61 Counter-stop 65 Holding body 66 Object 67 Bearing or support element A Axial direction B 1 Magnetic axis of the first fastening magnet B 2 Magnetic axis of the second fastening magnet B 3 Magnetic axis of the third fastening magnet FA Magnetic axial force FU Magnetic Circumferential force H 1 Magnet axis of the first mounting magnet H 2 Magnet axis of the second mounting magnet H 3 Magnet axis of the third mounting magnet L Common longitudinal axis L 1 First longitudinal axis L 2 Second longitudinal axis P Contact position R Target rotational position S Pivot axis U Circumferential direction

Claims

A sensing unit (27) for a measuring device (20), which is configured to sense a measured value at a measuring point of an object surface (21) in a contacting or contactless manner, wherein the sensing unit (27) comprises: - a carrier (28), - a sensing element (29) arranged on the carrier (28), which is configured to sense the object surface (21) in a contacting or contactless manner, - a fastening device (31) provided on the carrier (28), which is configured to be mechanically connected to a holder (26) of the measuring device (20), wherein the fastening device (31) comprises an abutment unit (32), which defines a first longitudinal axis (L1), which comprises an abutment surface (34), which defines a conical surface area around the first longitudinal axis (L1) and which is configured to be connected mechanically to a holder (26) of the measuring device (20), in an abutment position (P) on a counter abutment unit (51) of the holder (26) of the measuring device (20), so that a rotational degree of freedom in a circumferential direction (U) about the first longitudinal axis (L1) remains between the fastening device (31) and the holder (26), and wherein the fastening device (31) has at least one fastening magnet (40, 41, 42) which is configured to cooperate with a respective holder magnet (55, 56, 57) of the holder (26) in the abutment position (P), such that a magnetic axial force (FA) parallel to the first longitudinal axis (L1) is generated between the fastening device (31) and the holder (26), and such that a magnetic circumferential force (FU) is generated between the fastening device (31) and the holder (26) in a circumferential direction (U) about the first longitudinal axis (L1) until a predefined desired rotational position (R) about the first longitudinal axis (L1) is reached between the fastening device (31) and the holder (26), wherein the fastening device (31) has a stop surface (43) which, in the desired rotational position (R), bears against a counterstop surface (60) of the holder (26) in such a way that an offset between magnetic axes (B1, B2, B3) of the fastening magnets (40, 41, 42) and magnetic axes (H1, H2, H3) of the holding magnets (55, 56, 57) is present, so that a remaining circumferential magnetic force (FU) urges the stop surface (43) against the counterstop surface (60).The sensing unit of claim 1, wherein the at least one mounting magnet (40, 41, 42) has a magnet axis (B1, B2, B3) oriented parallel to the first longitudinal axis (L1).Sensing unit according to one of the preceding claims, wherein the fastening device (31) has a plurality of fastening magnets (40, 41, 42) which are arranged distributed uniformly in the circumferential direction (U) about the first longitudinal axis (L1).The sensing unit according to claim 3, wherein the polarity of at least two of the existing fixing magnets (40, 41, 42) is opposite when viewed parallel to the first longitudinal axis (L1).Sensing unit according to one of the preceding claims, wherein the contact surface (34) is divided into a plurality of surface sections (34a) arranged at a distance from one another in the circumferential direction (U).Sensing unit according to claim 5, wherein the stop surface (34) is arranged in the circumferential direction (U) between two adjacent surface sections (34a).The sensing unit according to any one of the preceding claims, wherein the at least one fastening magnet (40, 41, 42) is arranged closer to the first longitudinal axis (L1) than the contact unit (32).Holder (26) of a measuring device (20) for attaching a probe unit (27) to the measuring device (20), which holder is configured to record a measured value at a measuring point of an object surface (21) in a contacting or contactless manner, wherein the holder (26) has: - a holding body (50), - a counter-contact unit (51), which is present on the holding body (50) and defines a second longitudinal axis (L2), which has a counter-contact surface (53), which defines a truncated cone lateral surface about the second longitudinal axis (L2) and which is configured to bear in a contact position (P) against a contact unit (32) of a fastening device (31) of a probe unit (27), such that a rotational degree of freedom about the second longitudinal axis (L2) remains between the fastening device (31) and the holder (26), and wherein the holder (26) has at least one holder magnet (55, 56, 57) which is configured to cooperate with a fastening magnet (40, 41, 42) of the fastening device (31) in the bearing position (P) in each case, such that a magnetic axial force (FA) parallel to the second longitudinal axis (L2) is generated between the holder (26) and the fastening device (31), and such that a magnetic circumferential force (FU) is generated between the holder (26) and the fastening device (31) in a circumferential direction (U) about the longitudinal axis (L) until a predefined setpoint rotational position (R) about the second longitudinal axis (L2) is reached between the holder (26) and the fastening device (31), wherein the fastening device (31) has a stop surface (34), which in the desired rotational position (R) bears against a counterstop surface (60) of the holder (26) in such a way that there is an offset between magnet axes (B1, B2, B3) of the fastening magnets (40, 41, 42) and magnet axes (H1, H2, H3) of the holder magnets (55, 56, 57), such that a remaining magnetic circumferential force (FU) urges the stop surface (43) against the counterstop surface (60).The holder according to claim 8, wherein the at least one holder magnet (55, 56, 57) has a magnet axis (H1, H2, H3) which is oriented parallel to the second longitudinal axis (L2).Holder according to Claim 8 or 9, wherein a plurality of holder magnets (55, 56, 57) are present, which are arranged uniformly distributed about the second longitudinal axis (L2) in the circumferential direction (U).The holder according to claim 10, wherein the polarity of at least two of the existing holder magnets (55, 56, 57) is opposite when viewed parallel to the second longitudinal axis (L2).The holder according to any one of claims 8 to 11, wherein the at least one holder magnet (55, 56, 57) is arranged closer to the second longitudinal axis (L2) than the counter abutment unit (51).Arrangement comprising a scanning unit (27) according to one of Claims 1 to 7 and a holder (26) according to one of Claims 8 to 12 of a measuring device (20), wherein the measuring device (20) is configured to record a measured value at a measuring point of an object surface (21) in a touching or contactless manner.

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