SURFACE MEASURING DEVICE

Description

[0001] The invention relates to a surface measuring instrument of the type mentioned in the preamble of claim 1.

[0002] Surface measuring instruments of this type, such as tactile surface measuring instruments and especially roughness measuring instruments, are generally known. They comprise a base body and a probe that is movable along a feed axis by means of a feed device for probing the surface of a component to be measured. To measure a component, the probe is moved along the feed axis by means of the feed device, whereby a stylus element of the probe arm scans the surface, for example, and especially mechanically, by means of a stylus body arranged on a pivotably mounted probe arm.

[0003] To fulfill different measurement tasks, it is desirable to rotate the probe arm around a rotation axis running in the longitudinal direction of the probe arm, in order, for example, to probe a rotationally symmetrical component in the form of a shaft at different points in the circumferential direction, for example in the form of probe sections running in the axial direction of the shaft.

[0004] Surface measuring instruments are known with a probe holder for a probe of the surface measuring instrument, rotatably mounted relative to a base body about a rotational axis and rotatably positionable by means of an electromechanical drive train. When the probe holder, and thus the probe, is rotated about the rotational axis, the respective rotational position must be reproducible and maintained without backlash.

[0005] To ensure that the respective rotational position is maintained without backlash, the electromechanical drive train between the drive train's electric motor and the rotatably mounted probe holder must be designed to be backlash-free within the required reproducibility parameters. Such backlash-free drive trains are complex to manufacture and incur high costs, which is particularly true for backlash-free gearboxes.

[0006] Surface measuring instruments are also known in which the required reproducibility is achieved by having the electromechanical drive train rotate the probe holder against the action of a brake. In one such embodiment, heat is generated at the point of brake engagement, which is undesirable in a measuring instrument to avoid thermal effects. Furthermore, the use of a brake requires a drive train with a correspondingly high torque.

[0007] DE 28 11 969 A1 discloses a measuring device for measuring tapered roller bearings in which a radial probe head can be locked in two positions offset by 90°.

[0008] DE 37 89 875 T2 discloses a surface measuring instrument with the features of the preamble of claim 1.

[0009] The invention is based on the objective of providing a surface measuring instrument of the type mentioned in the preamble of claim 1, which is improved compared to known surface measuring instruments.

[0010] This problem is solved by the invention specified in claim 1.

[0011] The invention provides that the drive train has a worm gear and that locking means for locking the button holder in predefined rotational positions are assigned to the button holder.

[0012] The basic idea of ​​the invention is to deliberately forgo a highly backlash-free gearbox, which is complex and therefore expensive to manufacture, in order to reduce the production costs of the surface measuring instrument, and instead to use a worm gear that, while containing some backlash, is cost-effective. Based on this, the required reproducibility in the rotary positioning of the probe holder is achieved according to the invention by providing detent devices by means of which the probe holder is locked in predefined rotational positions relative to the base body. Such detent devices can also be implemented simply and therefore cost-effectively.

[0013] The invention provides that the locking means comprise a first component and a second component, one of which is rotationally fixed to the stylus holder and the other rotationally fixed to the base body. One of the components has at least one locking element, and the other component has a plurality of locking recesses spaced apart from one another in the circumferential direction of the axis of rotation. Each of these recesses defines one of the predefined rotational positions of the stylus holder relative to the base body, and the locking element engages in each of these positions. In this way, the locking means are designed to be particularly simple and cost-effective.

[0014] According to the invention, the play in the drive train is eliminated by the locking mechanism.

[0015] The invention thus provides a surface measuring instrument with an electromechanically rotatable probe holder, which is simple and cost-effective in its construction as well as robust and at the same time ensures high positioning accuracy and reproducibility when rotating the probe holder around the axis of rotation.

[0016] A further advantage of the surface measuring instrument according to the invention is that the assembly of the electromechanical drive train during the manufacturing of the surface measuring instrument is simple. Furthermore, the invention enables the retrofitting of surface measuring instruments in which the rotation of the probe holder is done manually at the factory.

[0017] The surface measuring device according to the invention can, for example, be a tactile surface measuring device.

[0018] The axis of rotation around which the probe holder is rotatably mounted relative to the base body preferably runs parallel to the feed axis of a feed device of the surface measuring instrument or parallel to the longitudinal direction of a probe arm of the probe.

[0019] Advantageously, the locking recesses for locking the button holder are designed to be complementary to the locking element, at least in sections.

[0020] In order to achieve a simple design of the locking means, another advantageous embodiment of the invention provides that the locking element is movably mounted in one locking direction.

[0021] A particularly advantageous embodiment of the invention provides that the detent element is pre-tensioned in the detent direction by spring means. In this embodiment, the detent element engages in the respective detent recesses under spring pressure and is released by the drive torque of the electric motor of the electromechanical drive train against the pre-tension of the spring means.

[0022] The design of the locking element can be selected according to the specific requirements within wide limits. An advantageous embodiment of the invention provides that the locking element comprises a ball. Suitable balls are available as high-precision machined, yet very cost-effective standard components and ensure a precisely defined geometry during locking.

[0023] Another advantageous embodiment of the invention provides that the detent element is arranged relative to the detent recesses such that the detent direction is parallel to the axis of rotation, such that the detent element moves parallel to the axis of rotation when detenting or disengaging. To make the detent and disengagement process simple and reliable, another advantageous embodiment with spring means provides that the spring load of the detent element is selected relative to the drive torque of an electric motor of the electromechanical drive train such that the detent element disengages when the first component is rotated relative to the second component by the electric motor.

[0024] Another advantageous embodiment of the invention provides that the locking element is movably connected to the associated component by means of a holder.

[0025] A further development of the aforementioned embodiment provides that the holder is formed by a leaf spring. In this embodiment, the leaf spring performs a holding function for the detent element. Simultaneously, the detent element is spring-loaded in the detent direction by the leaf spring. In addition to the leaf spring, however, further spring elements, for example in the form of a compression spring, particularly a coil spring, can be provided to create a preload in the detent direction.

[0026] To prevent the rotational stroke from being limited when the probe holder is rotated about the axis of rotation, another advantageous development of the invention provides that slip ring contacts are provided for transmitting output signals from a probe attached to the probe holder to an evaluation device of the surface measuring instrument.

[0027] Another advantageous embodiment of the invention provides that the worm gear comprises a worm connected to an electric motor of the electric motor drive train, which meshes with a worm wheel. In this case, it is generally sufficient if the reduction of the drive speed of the electric motor is achieved exclusively by the worm gear, thus eliminating the need for further gear elements in the drive train.

[0028] In order to simplify the design of the drive train, an advantageous further development of the invention provides that the worm gear is connected in a rotationally fixed manner to a rotatably mounted shaft, which defines the axis of rotation.

[0029] Advantageously, the worm gear is a self-locking worm gear, as provided for in another advantageous embodiment of the invention.

[0030] The invention is explained in more detail below with reference to the attached schematic drawing and an exemplary embodiment.

[0031] It shows: Fig. 1 in a schematic perspective view shows an embodiment of a surface measuring instrument according to the invention, wherein a housing of the surface measuring instrument is omitted for illustrative purposes, Fig. 2 in the same representation as Fig. 1 the embodiment according to Fig. 1 from a different perspective, Fig. 3 in the same representation as Fig. 1 the embodiment according to Fig. 1 , whereas opposite Fig. 1 Components are omitted; Fig. 4 schematically illustrates the embodiment in a partially cutaway perspective view according to Fig. 1 , Fig. 5 in the same representation as Fig. 4 the embodiment according to Fig. 1 , whereas opposite Fig. 4 Components are omitted, Fig. 6 in the same representation as Fig. 5 from another perspective the exemplary embodiment according to Fig. 1 and Fig. 7 in the same representation as Fig. 6 a detail from Fig. 6 in the area of ​​a grid element.

[0032] The following refers to Fig. 1 bis Fig. 7 An embodiment of a surface measuring device according to the invention is explained in more detail.

[0033] Fig. 1 Figure 1 shows a schematic perspective view of an embodiment of a surface measuring instrument 2 according to the invention, which has a base body 4. The base body 4 has a base plate 6, on which the components of the surface measuring instrument 2 are mounted, and a housing, which is omitted from the drawing for illustrative purposes. In the illustrated embodiment, the surface measuring instrument 2 is designed as a tactile surface measuring instrument. The structure and function of corresponding surface measuring instruments are generally known to those skilled in the art and are therefore only explained in more detail here to the extent necessary to explain the invention.

[0034] The surface measuring instrument 2 has a probe holder 10 for a probe of the surface measuring instrument 2, which is rotatably mounted relative to the base body 4 about a rotational axis and can be positioned by means of an electromechanical drive train 8. For the sake of simplicity, the probe is not shown in the drawing. Details of the probe holder are described in particular in the Figuren 2 and 4 The design and function of such a push-button holder are generally known to experts and are therefore not explained in detail here.

[0035] The axis of rotation about which the button holder 10 is rotatably mounted relative to the base body 4 is defined by a rotatably mounted shaft 12 (see Figure 1). Fig. 4 ) defined, which is rotatably mounted on the base body 4 via ball bearings 14, 16 and is non-rotatably connected to the button holder 10.

[0036] The rotatably mounted shaft 12 is connected to an electric motor 18 via the electromechanical drive train 8.

[0037] According to the invention, the drive train 8 has a worm gear 20, wherein locking means 22 for locking the button holder 10 in predefined rotational positions relative to the base body 4 are assigned to the button holder 10.

[0038] The worm gear 20 has a worm 24 which is non-rotatably connected to an output shaft of the electric motor 18 and which engages with a worm wheel 26 (see figure). Fig. 3 ), which is non-rotatably connected to shaft 12 (see Fig. 4 In the illustrated embodiment, the worm gear 20 is designed to be self-locking. According to the direction of rotation of the output shaft of the electric motor 18, the shaft 12 and thus the button holder 10 can be rotated about the axis of rotation defined by the shaft 12.

[0039] The power supply and control elements of the electromechanical drive train 8 are not shown in the drawing. However, the design of such power supply and control elements is generally known to those skilled in the art.

[0040] In the illustrated embodiment, the locking means 22 have a first component 28 and a second component 30 (see below). Fig. 4 ) one of which, namely component 30, is rotationally fixed to the button holder 10 and the other, namely component 28, is rotationally fixed to the base body 4. Component 28 has a detent element 32 in the form of a ball (see in particular ). Fig. 7 ) arranged. On the other component 30, a plurality of detent recesses spaced apart from each other in the circumferential direction of the axis of rotation are formed (cf. Fig. 5 ), each of which defines one of the predefined rotational positions of the probe holder 10 relative to the base body and into which the detent element 32 engages in the respective rotational position of the probe holder 10 relative to the base body 4. Fig. 5 is merely a recess marked with reference numeral 34.

[0041] As especially from Fig. 5 As can be seen, the second component has a disc-shaped section 36 in which openings are formed that constitute the locking recesses 34. To lock the second component 30 with the first component 28 and thus to lock the stylus holder 10 with the base body 4, the locking recesses 34 are shaped at least partially complementarily to the locking element 32.

[0042] The locking element 32, designed as a ball, is in Fig. 6 and especially in Fig. 7 The locking element 32 is movably connected to the component 28 by means of a holder, which in the illustrated embodiment is formed by a leaf spring 38. The leaf spring 38 serves both as a holder for the locking element 32 and as a preload on the locking element 32 in the direction of the opposite disc-shaped section 36 of the component 30.

[0043] The detent element 32 is pre-tensioned by a spring in the form of a compression spring 40 designed as a helical spring and, in the illustrated embodiment, is movably mounted in a detent direction. In the illustrated embodiment, the detent element 32 is arranged relative to the detent recesses 34 such that the detent direction is parallel to the axis of rotation and the detent element 32 moves parallel to the axis of rotation when detenting or detenting.

[0044] In a modification of the embodiment shown in the drawing, the locking element can also be movably mounted in the radial direction of the axis of rotation, whereby the locking recesses can then be formed, for example, spaced apart from each other in the circumferential direction in the outer circumferential surface of a roller-like section of the second component 30.

[0045] The step size during the rotary positioning of the probe holder 10 relative to the base body 4 is defined by the distance between the detent recesses 34 in the circumferential direction of the axis of rotation. To reduce the step size during rotary positioning, in the illustrated embodiment, further detent recesses with an associated detent element can be provided in the disk-shaped section 36, radially offset from the detent recesses 34. These further detent recesses are then arranged circumferentially offset from the detent recesses 34.

[0046] The preload of the detent element 32, caused primarily by the compression spring 40, in the direction of the detent recesses 34, is selected relative to the drive torque of the electric motor 18 such that, when the first component 28 is rotated relative to the second component 30, the detent element is pushed out of the respective detent recess 34 by the electric motor 18 against the preload of the spring means and is thereby disengaged.

[0047] Slip ring contacts 42 are provided for transmitting output signals from a push button attached to the push button holder 10 to an evaluation device arranged on the base body 4 or externally to the surface measuring device 2 (see figure). Fig. 4 and Fig. 6 In this way, the button holder 10 can be rotated endlessly in any direction relative to the base body 4.

[0048] The operating principle of the surface measuring instrument 2 according to the invention is as follows: To measure the surface of a workpiece using the surface measuring instrument 2, a tactile probe, for example, is attached to the probe holder 10, by means of which the surface of the workpiece is probed with a stylus. By moving the stylus along a feed axis by means of a feed device of the surface measuring instrument 2, the workpiece is scanned, for example, when measuring a shaft in its axial direction.

[0049] In order to repeat the measurement in the circumferential direction of the shaft at a different location, the rotational position of the probe holder 10 and thus of the probe relative to the base body 4 is changed.

[0050] To rotate the probe holder 10, the electric motor 18 drives the worm gear 20 such that the shaft 12, and thus the probe holder 10, which is non-rotatably connected to the shaft 12, rotates about the axis of rotation defined by the shaft 12. During the rotation of the probe holder 10 about the axis of rotation, the detent element 32 is pushed out of a detent recess against the preload of the spring elements, moves circumferentially around the axis of rotation relative to the disc-shaped section 36, and engages in the next detent recess in the circumferential direction. The process of disengaging from one detent recess 34 and engaging in the next detent recess in the circumferential direction is repeated until the desired rotational position of the probe holder 10 is reached and the electric motor 18 is stopped.

[0051] In the rotational position then reached, the button holder 10 is locked to the base body 4 and thus connected to the base body 4 without play. The locking mechanism provided according to the invention eliminates any mechanical play in the electromechanical drive train 8.

[0052] Due to the combination of a backlash-prone worm gear with detent devices that eliminate the backlash, the invention provides a surface measuring instrument that, with a simple and cost-effective design, enables precise rotary positioning of the probe holder with high reproducibility. Bezugszeichenliste

[0053] 2 Surface measuring device 4 Base body 6 Base plate 8 Electromotive drive train 10 Pushbutton holder 12 Shaft 14 Ball bearing 16 Ball bearing 18 Electric motor 20 Worm gear 22 Detent 24 Worm 26 Worm wheel 28 1st component 30 2nd component 32 Detent element 34 Detent recess 36 Disc-shaped section 38 Leaf spring 40 Compression spring 42 Slip ring contacts

Claims

1. Surface measuring device (2), with a base body (4) and with a probe carrier (10) mounted rotatably about an axis of rotation relative to the base body (4) and rotatably positionable by an electromotive drive train (8) for a probe of the surface measuring device, wherein the drive train (8) has a worm gear (20), characterized in that latching means (22) for latching the probe carrier (10) in predetermined rotational positions are associated with the probe carrier (10) and the latching means (22) have a first component (28) and a second component (30), one of which is connected to the probe carrier (10) in a rotationally fixed manner and the other of which is connected to the base body (4) in a rotationally fixed manner, wherein at least one latching element (32) is formed on at least one of the components (28, 30) and a plurality of latching recesses (34) spaced apart from one another in the circumferential direction of the axis of rotation are formed on the other component, each of which defines one of the predetermined rotational positions of the probe carrier (10) relative to the base body (4) and in which the latching element latches in the respective rotational position of the probe carrier (10) relative to the base body (4).

2. Surface measuring device according to Claim 1, characterized in that the latching recesses (34) for latching the probe carrier (10) are formed at least in sections in a complementary manner to the latching element (32).

3. Surface measuring device according to Claim 1 or 2, characterized in that the latching element (32) is mounted movably in a latching direction.

4. Surface measuring device according to one of the preceding claims, characterized in that the latching element (32) is prestressed in the latching direction by spring means.

5. Surface measuring device according to one of the preceding claims, characterized in that the latching element (32) has a ball.

6. Surface measuring device according to one of the preceding claims, characterized in that the latching element (32) is arranged with respect to the latching recesses (34) in such a way that the latching direction runs parallel to the axis of rotation and the latching element (32) moves parallel to the axis of rotation during latching or unlatching.

7. Surface measuring device according to Claim 5 or 6, characterized in that the preload of the latching element (32) with respect to the drive torque of an electric motor (18) of the electromotive drive train (8) is selected in such a way that the latching element (32) is unlatched by the electric motor (18) during rotation of the first component (28) relative to the second component (30).

8. Surface measuring device according to one of the preceding claims, characterized in that the latching element (32) is connected movably to the associated component by means of a carrier.

9. Surface measuring device according to Claim 8, characterized in that the carrier is formed by a leaf spring (38).

10. Surface measuring device according to one of the preceding claims, characterized in that slip ring contacts (42) are provided for transmitting the output signals from a probe which is fastened to the probe carrier to an evaluation device of the surface measuring device.

11. Surface measuring device according to one of the preceding claims, characterized in that the worm gear (20) has a worm (24) which is rotationally drive-connected to an electric motor (18) of the electromotive drive train (8) and which is in engagement with a worm wheel (26).

12. Surface measuring device according to Claim 11, characterized in that the worm wheel (26) is connected in a rotationally fixed manner to a rotatably mounted shaft (12) which defines the axis of rotation.