CARRIER FOR A POSITION MEASURING DEVICE

Description

FIELD OF TECHNOLOGY

[0001] The present invention relates to a driver for a position measuring device according to the preamble of claim 1. STATE OF THE ART

[0002] EP 2 781 890 A1 discloses a position measuring device, in particular a length measuring device. The position measuring device comprises a scale in a housing that accommodates the scale, and a scanning unit that scans the scale. The scanning unit is coupled to a driver. The driver can be attached to an object to be measured.

[0003] Another length measuring device with a driver is known from DE 27 29 708 B1.

[0004] DE 100 18 269 A1 discloses a driver according to the preamble of claim 1.

[0005] DE 20 2006 010305 U1 discloses a position measuring device with a driver having a groove for receiving a cable. SUMMARY OF THE INVENTION

[0006] The present invention is based on the object of specifying a driver for a position measuring device, wherein the driver has a flexible structure adapted to a cable of a scanning unit of the position measuring device.

[0007] This object is achieved according to the invention by the driver for a position measuring device having the features of claim 1.

[0008] The driver according to the invention is designed to support a scanning unit of the position-measuring device. The driver has an opening for receiving and guiding through a cable of the scanning unit. The opening extends through at least part of the driver. The driver has a recess provided in a longitudinal section of the driver for laterally inserting the cable into the driver. The driver has a closure element corresponding to the recess. The closure element is detachably connected to a part of the driver that is complementary to the closure element. The driver has a first inner contour. The closure element has a second inner contour opposite the first inner contour. The first inner contour and the second inner contour each extend through the longitudinal section of the driver.The first inner contour and the second inner contour form the opening for receiving and passing through the cable.

[0009] The driver is particularly designed such that the cable can be guided through at least part of the driver (e.g., the sword-shaped center piece). Thus, the driver includes a cable feedthrough for the cable of the scanning unit.

[0010] The driver preferably has an adapter piece for connecting the scanning unit to the driver. The adapter piece enables adjustment or alignment of the scanning unit relative to a scale to be scanned. This adjustment or alignment can be performed in several degrees of freedom (e.g., distance / parallelism, moiré angle, and / or height).

[0011] It is advantageous if the closure element is designed to provide strain relief for the cable when connected.

[0012] Preferably, the opening has a round, square or rectangular cross-section.

[0013] A position measuring device with a driver according to the invention is specified in claim 13. The position measuring device is in particular an encapsulated length measuring device with a one-piece or two-piece housing.

[0014] The invention achieves an adaptation of the carrier to the cable (e.g. geometry, shape) of the scanning unit. For this purpose, in particular a cable feedthrough in the form of an opening is provided in the carrier. The carrier is advantageously suitable for the precise reception and passage of the cable through it. In contrast to a conventional design, in which a flexible conductor is typically used as a carrier for a connecting cable, the invention enables it to be used in particular with larger dimensions (i.e. larger cable diameter or larger cable size). This in turn enables a flexible design of the carrier. The invention also enables the cable of the scanning unit to be connected to a plug connection provided separately from the carrier.

[0015] Advantageous embodiments of the invention can be found in the dependent claims.

[0016] Further details and advantages of the present invention are explained in the following description of possible embodiments of the invention in conjunction with the figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] It shows Figure 1 shows a perspective view of an exemplary position measuring device; Figure 2 shows a cross-sectional view of the position measuring device according to Figure 1 ; Figure 3a a perspective view of an end side of the position measuring device according to Figure 1 ; Figure 3b shows a perspective exploded view of the end face of the position measuring device according to Figure 1 ; Figure 4 a cross-sectional view of the end face of the position measuring device according to Figure 1 in the area of ​​a second (upper) sealing cord; Figure 5a a perspective view of a driver of the position measuring device according to Figure 1 ; Figure 5b a perspective view of the driver according to Figure 5awith a closure element detached from a complementary part of the driver; Figure 6a a plan view of the driver according to Figure 5a to illustrate an L-shaped section; Figure 6b a cross-sectional view of the driver according to Figure 5a in the central area of ​​the driver; Figure 7 a perspective view of the closure element according to Figure 5b ; and Figure 8 is an exploded perspective view of the position measuring device according to Figure 1 . DESCRIPTION OF THE EMBODIMENTS

[0018] Identical elements or functionally identical elements are provided with the same reference numerals in the figures.

[0019] An example of implementation is shown below using the Figures 1 to 8explained. The position measuring device according to the exemplary embodiment comprises a base body 1 (e.g. machine bed or base body of the machine), a first housing part 10.1 extending in a longitudinal direction X and connected to the base body 1, and a second housing part 10.2 extending in the longitudinal direction X and connected to the base body 1 (cf. Figure 8 ). A hollow profile 10 is formed by at least the first housing part 10.1 and the second housing part 10.2 (cf. Figure 2 ). The position measuring device has a scale 12 arranged within the hollow profile 10 and a scanning unit 14 opposite the scale 12 for scanning the scale 12. The base body 1 and the scale 12 are directly connected to one another.

[0020] As in Figure 2As shown, scale 12 borders on a mounting surface 1.1 of base body 1. The mounting surface 1.1 is a lateral surface of base body 1 facing scale 12.

[0021] The position measuring device is, in particular, a length measuring device. For this purpose, the scale 12 and the scanning unit 14 are movable relative to each other in the longitudinal direction X (i.e., the measuring direction). During the position measurement, the scanning unit 14 scans a measuring graduation of the scale 12 and generates position measurement values ​​from it. The measuring graduation is not shown in the figures.

[0022] The base body 1 and the first housing part 10.1 are directly connected to each other via fastening screws. Figure 2 One of these fastening screws (fastening screw 4.11) is visible. Furthermore, the base body 1 and the second housing part 10.2 are directly connected to each other via fastening screws 4.2. Figure 2One of these fastening screws 4.2 (fastening screw 4.21) is visible. The fastening screw 4.21 is assigned to the fastening screw 4.11, i.e., the fastening screws 4.11 and 4.21 are arranged one above the other in the Z direction. The Z direction runs perpendicular to the longitudinal direction X and parallel to the mounting surface 1.1 of the base body 1. In the following, the Z direction is also referred to as the "first direction."

[0023] Directly connected means that the respective elements are connected directly, i.e. not via one or more intermediate elements.

[0024] With reference to Figure 2The hollow profile 10 is formed in its entirety by the base body 1, the first housing part 10.1 and the second housing part 10.2. Extending in the longitudinal direction X, the position measuring device has a first sealing lip 18.1 and a second sealing lip 18.2 (hereinafter referred to as sealing lips 18). The sealing lips 18 are arranged at the lower end of the hollow profile 10. A driver 16, which carries the scanning unit 14, engages through the sealing lips 18. Further details on the driver 16 will be described later in connection with Figures 5 to 7 (or 8) described.

[0025] As in Figure 2 As shown, the sealing lips 18 are positioned opposite each other in the Y direction. The Y direction runs perpendicular to the mounting surface 1.1 of the base body 1. In the following, the Y direction is also referred to as the "second direction."

[0026] With reference to Figure 2the first housing part 10.1 has a first section 10.11 for fastening the first housing part 10.1 to the base body 1. Furthermore, the second housing part 10.2 has a second section 10.21 facing the base body 1 for fastening the second housing part 10.2 to the base body 1. The first section 10.11 is arranged on a first (lower) side of the scale 12. The second section 10.21 is arranged on a second (upper) side of the scale 12 opposite the first side. The first section 10.11 and the second section 10.21 are arranged opposite each other in the first direction (ie Z-direction). As in Figure 2As shown, the fastening screw 4.11 extends through the first section 10.11. Furthermore, the fastening screw 4.21 extends through the second section 10.21. The two-part housing formed by the first and second housing parts 10.1, 10.2 thus extends on both sides of the scale 12 to the base body 1 and surrounds the scale 12 on the upper and lower sides.

[0027] The position measuring device has a first to fourth sealing element 20.1 to 20.4 (cf. Figure 2 and 8 ). As in Figure 2 As shown, the first housing part 10.1 has a first recess 11.1 adjacent to the base body 1 for receiving the first sealing element 20.1. Furthermore, the second housing part 10.2 has a second recess 11.2 adjacent to the base body 1 for receiving the second sealing element 20.2. The first recess 11.1 and the second recess 11.2 each extend in the longitudinal direction X.

[0028] For example, the first sealing element 20.1 is a first sealing cord. Furthermore, the second sealing element 20.2 is, for example, a second sealing cord. The first sealing element 20.1 and the second sealing element 20.2 each extend in the longitudinal direction X. The first and second sealing elements 20.1, 20.2 are each received by the first and second recesses 11.1, 11.2 over their entire length.

[0029] By means of the first and second sealing elements 20.1, 20.2, the two-part housing formed by the first and second housing parts 10.1, 10.2 can be sealed laterally, ie in the Y-direction, against the base body 1. This is shown in Figure 2 illustrated.

[0030] The position measuring device has a first cover element 10.3 arranged at a first end section A, A' of the first and second housing parts 10.1, 10.2 and a second cover element 10.4 arranged at a second end section B, B' of the first and second housing parts 10.1, 10.2 opposite the first end section A, A' (cf. Figure 8 ). As in Figure 8 As can be seen, the third sealing element 20.3 is arranged between the first end section A, A' and the first cover element 10.3. Furthermore, the fourth sealing element 20.4 is arranged between the second end section B, B' and the second cover element 10.4. In particular, the third sealing element 20.3 and the fourth sealing element 20.4 are each plate-shaped. Furthermore, in Figure 8 It can be seen that the first and second cover elements 10.3, 10.4 can each be connected to the base body 1 via a fastening screw 4.41, 4.42 (fastening screws 4.4).

[0031] The third sealing element 20.3 and the fourth sealing element 20.4 can each also be referred to as a (compressible) sealing plate.

[0032] The first and second cover elements 10.3, 10.4 represent a third and fourth housing part (end housing parts) respectively. This is shown in Figure 1 illustrated. By means of the third and fourth sealing elements 20.3, 20.4, the housing formed by the first to fourth housing parts 10.1 to 10.4 can be sealed at each end, ie at the first end section A, A' or at the second end section B, B'.

[0033] Figure 3a shows one end side of the position measuring device Figure 1 . In Figure 3a In particular, the first end section A' of the second housing part 10.2 and the first cover element 10.3 (third housing part) are shown. Figure 3b shows the third sealing element 20.3 arranged between the second and third housing parts 10.2, 10.3. In the cross-sectional view of Figure 4 The second and third sealing elements 20.2, 20.3 can be seen. As in Figure 4 As shown, the second and third sealing elements 20.2, 20.3 are each arranged flush with the mounting surface 1.1 of the base body 1. This achieves the lateral sealing of the housing towards the base body 1. In Figure 4 This is for the Figure 3a The situation is analogous for the opposite end of the position measuring device.

[0034] With reference to Figure 2 The first housing part 10.1 has a third recess 11.3 for receiving the first sealing lip 18.1. Furthermore, the second housing part 10.2 has a third section 10.22 facing away from the base body 1. The first housing part 10.1 and the third section 10.22 are arranged opposite each other in the second direction (Y-direction). As shown in Figure 2As shown, the second housing part 10.2 has a fourth recess 11.4 arranged in the third section 10.22 for receiving the second sealing lip 18.2. The third recess 11.3 and the fourth recess 11.4 each extend in the longitudinal direction X. The first and second sealing lips 18.1, 18.2 are each received by the third and fourth recess 11.3, 11.4 over their entire length. The sealing lips 18 serve to seal the hollow profile 10 formed by the base body 1, the first housing part 10.1 and the second housing part 10.2 downwards, i.e. in the (negative) Z-direction (cf. Figure 2 ).

[0035] The first to fourth sealing elements 20.1 to 20.4, in conjunction with the sealing lips 18, provide essentially complete sealing of the position measuring device. Overall, this results in a system sealed against a fluid (e.g., cooling lubricant).

[0036] The position measuring device is in particular an encapsulated, unguided system. The scanning unit 14 is movable relative to the hollow profile 10 in the longitudinal direction X, in particular independently of the scale 12 and independently of the first and second housing parts 10.1, 10.2 (cf. Figure 2 ). As in Figure 2 As shown, the scanning unit 14 has no common guide surface with the scale 12 or with the first and second housing parts 10.1, 10.2.

[0037] In the Figures 5 to 7 (or 8) further details of the driver 16 are explained. According to Figure 8 The driver 16 has a mounting area 16.1. The mounting area 16.1 serves to connect the driver 16 with an object 2 to be measured. As in Figure 8As shown, the driver 16 can be connected to the object 2 to be measured via fastening screws 4.3. Furthermore, the driver 16 has a sword-shaped center piece 16.2, an adapter piece 16.3, and a closure element 16.4. The adapter piece 16.3 serves to connect the scanning unit 14 to the sword-shaped center piece 16.2. The adapter piece 16.3 allows the scanning unit 14 to be adjusted relative to the scale 12 in several degrees of freedom (e.g., degrees of freedom Y, RY, Z). The sword-shaped center piece 16.2 connects the adapter piece 16.3 and the mounting area 16.1.

[0038] As in Figure 2 As shown, the sword-shaped center piece 16.2 extends from the interior of the hollow profile 10 through the sealing lips 18 to the mounting area 16.1 arranged outside the hollow profile 10. The scanning unit 14 comprises a cable 14.1 (cf. Figure 8). The cable 14.1 has an upper section 14.11 and a lower section 14.12. The upper section 14.11 extends from the scanning unit 14 to the sword-shaped center piece 16.2. The lower section 14.12 is led out of the mounting area 16.1 in the longitudinal direction (X direction) (cf. Figure 2 and 8 ).

[0039] The driver 16 serves in particular to carry the scanning unit 14. With reference to Figure 5a The driver 16 has an opening 17 for receiving and passing through the cable 14.1. The opening 17 extends through at least a part of the driver 16 (cf. Figure 6b ). This allows the cable 14.1 to be guided through at least part of the driver 16, in particular the sword-shaped center piece 16.2.

[0040] With respect to the geometry of the driver 16, the longitudinal direction (X direction) corresponds to a direction parallel to a longitudinal extension of the driver 16. Furthermore, the first direction (Z direction) corresponds to a direction perpendicular to a base surface G of the driver 16. Furthermore, the second direction (Y direction) corresponds to a direction perpendicular to the longitudinal extension of the driver 16 and parallel to the base surface G of the driver 16.

[0041] With reference to Figure 5a and 6b The driver 16 is designed such that the cable 14.1 can be guided through the sword-shaped center piece 16.2 in the first direction (Z direction). Furthermore, the driver 16 is designed such that the cable 14.1 can be guided through the mounting area 16.1 in the longitudinal direction (X direction) in a longitudinal section L of the driver 16.

[0042] With reference to Figure 6aThe sword-shaped center piece 16.2 has a first dimension L1 in the second direction (Y direction). For example, the first dimension L1 lies in a range from 1.0 times to 1.5 times or in the range from 1.0 times to 1.25 times a diameter D of the cable 14.1. Thus, the first dimension L1 is greater, in particular slightly greater, than or equal to the diameter D of the cable 14.1. The first dimension L1 (i.e., width of the sword-shaped center piece 16.2) is thus adapted such that the cross-section of the cable 14.1 can be accommodated by the sword-shaped center piece 16.2.

[0043] In Figure 5b It is shown that the driver 16 has a recess 16.4' provided in the longitudinal section L of the driver 16 for laterally inserting the cable 14.1 into the driver 16. With reference to Figure 6aThe recess 16.4' has a first section 20.1 (elongated hole) encompassing the opening 17 and a second section 20.2 adjacent to the first section 20.1. The first section 20.1 and the second section 20.2 form a section 20 that is L-shaped in a plan view of the driver 16. The first section 20.1 extends in the longitudinal direction (X direction). The second section 20.2 extends in the second direction (Y direction). The first section 20.1 is arranged in a central region Q of the driver 16. The second section 20.2 extends from a lateral surface 24 of the driver 16 to the central region Q of the driver 16.

[0044] Referring to Figure 6athe first subsection 20.1 has a second extension L2 in the second direction (Y direction). Furthermore, the second subsection 20.2 has a third extension L3 in the longitudinal direction (X direction). For example, the second extension L2 and / or the third extension L3 each lie in a range from 1.0 times to 1.25 times or in the range from 1.0 times to 1.15 times the diameter D of the cable 14.1. Thus, the second and third extensions L2 and L3 are each larger, in particular minimally larger, than or equal to the diameter D of the cable 14.1. This enables the cable 14.1 to be inserted laterally into the driver 16 via the L-shaped section 20.

[0045] With reference to Figure 5b the driver 16 has the closure element 16.4 corresponding to the recess 16.4' (see also Figure 7). The closure element 16.4 is detachably connected to a part C of the driver 16 that is complementary to the closure element 16.4. As shown in Figure 6b As shown, the driver 16 has a first inner contour 17.1. Furthermore, the closure element 16.4 has a second inner contour 17.2 opposite the first inner contour 17.1. The first inner contour 17.1 and the second inner contour 17.2 each extend through the longitudinal section L of the driver 16. The opening 17 for receiving and passing through the cable 14.1 is formed by the first inner contour 17.1 and the second inner contour 17.2.

[0046] In Figure 6bA cross-sectional plane S1 is shown, which runs parallel to a longitudinal extension of the driver 16 and perpendicular to the base area G of the driver 16. The cross-sectional plane S1 also runs through the cable 14.1 (or the opening 17). For example, the opening 17 formed by the first and second inner contours 17.1, 17.2 has an arcuate or angled profile. According to Figure 6b This course has an essentially L-shape.

[0047] In Figure 5b The locking element 16.4 is shown in the released state. The locking element 16.4 can be connected to the complementary part C of the driver 16 via fastening screws 4.5.

[0048] Referring to Figure 5b the recess 16.4' is designed such that, when the closure element 16.4 is released from the complementary part C (ie released state), the cable 14.1 can be inserted into the driver 16 in the second direction (Y direction).

[0049] The closure element 16.4 has a dual function. On the one hand, the closure element 16.4 serves to close the recess 16.4' (or the driver 16) after the cable 14.1 has been inserted laterally into the driver 16. On the other hand, the closure element 16.4 is designed to provide strain relief for the cable 14.1 when connected. Figure 7 the inner wall (second inner contour 17.2) of the closure element 16.4 is clearly visible.

[0050] The opening 17 has, for example, a round, square or rectangular cross-section. As in Figure 6bAs can be seen, the opening 17 has a fourth extension L4 in a plane S2. The plane S2 runs parallel to the base area G of the driver 16. For example, the fourth extension L4 lies in a range from 1.0 times to 1.25 times or in the range from 1.0 times to 1.15 times the diameter D of the cable 14.1. Advantageously, the cross section of the opening 17 is adapted to the cross section of the cable 14.1 (cf. Figure 6a ).

[0051] Preferably, the fourth dimension L4 is in a range of 2 mm to 20 mm or in the range of 5 mm to 15 mm.

[0052] The driver 16 is preferably part of the Figures 1 to 8 explained position measuring device (i.e., encapsulated length measuring device with the two-part housing). Alternatively, the driver 16 may also be suitable for use in an encapsulated length measuring device with a one-piece housing.

[0053] A parts kit for the Figures 1 to 8 The position measuring device described comprises the first housing part 10.1, which is connectable to the base body 1, and the second housing part 10.2, which is connectable to the base body 1. Furthermore, the set of parts includes the driver 16 for supporting the scanning unit 14.

[0054] Furthermore, the parts set can include the additional elements 10.1 to 10.4, 20.1 to 20.4, and 18 (complete parts set). By assembling the parts set, an existing open length measuring system (i.e., a system without encapsulation) consisting of the scale 12 and the scanning unit 14 can be encapsulated.

[0055] The invention has the following particular advantages. The kit is suitable for encapsulating any open length measuring system (universal applicability). This requires no changes to the assembly process or assembly method of the open length measuring system, nor does it require any redesign (e.g., special cable assembly). The simplified design of the position measuring device results in low system costs. It enables disassembly of the housing of the position measuring device (e.g., for cleaning) without misalignment.

[0056] The invention enables particularly high-resolution position measurement if the measuring graduation is designed to be optically scanned. Alternatively, the measuring graduation can also be designed to be magnetically, inductively, or capacitively scanned.

Claims

1. Driver (16) for a position measuring device, wherein the driver (16) is designed to carry a scanning unit (14) of the position measuring device, wherein the driver (16) has an opening (17) for the receiving and guiding through of a cable (14.1) of the scanning unit (14), wherein the opening (17) extends through at least part of the driver (16), characterized in that the driver (16) has a cutout (16.4') provided in a longitudinal section (L) of the driver (16) for laterally placing the cable (14.1) into the driver (16), in that the driver (16) has a closure element (16.4) corresponding to the cutout (16.4'), in that the closure element (16.4) is releasably connected to a part (C) of the driver (16) that is complementary to the closure element (16.4), in that the driver (16) has a first inner contour (17.1), in that the closure element (16.4) has a second inner contour (17.2) opposite the first inner contour (17.1), in that the first inner contour (17.1) and the second inner contour (17.2) each extend through the longitudinal section (L) of the driver (16), and in that the opening (17) for the receiving and guiding through of the cable (14.1) is formed by the first inner contour (17.1) and the second inner contour (17.2).

2. Driver (16) according to Claim 1, wherein the driver (16) has a blade-shaped central piece (16.2), wherein the driver (16) is designed in such a manner that the cable (14.1) can be guided through the blade-shaped central piece (16.2) in a first direction (Z) which runs perpendicularly to a base area (G) of the driver (16).

3. Driver (16) according to Claim 2, wherein the blade-shaped central piece (16.2) has a first extent (L1) in a second direction (Y) which runs perpendicularly to a longitudinal extent of the driver (16) and parallel to the base area (G) of the driver (16), the first extent (L1) lying in a range from 1.0 to 1.5 times or in the range from 1.0 to 1.25 times a diameter (D) of the cable (14.1).

4. Driver (16) according to one of the preceding claims, wherein the cutout (16.4') has a first subsection (20.1) surrounding the opening (17) and a second subsection (20.2) adjacent to the first subsection (20.1), wherein a section (20) of L-shaped design in a top view of the driver (16) is formed by the first subsection (20.1) and the second subsection (20.2), wherein the first subsection (20.1) extends in a longitudinal direction (X) which runs parallel to a longitudinal extent of the driver (16), wherein the second subsection (20.2) extends in a second direction (Y) which runs perpendicularly to the longitudinal extent of the driver (16) and parallel to a base area (G) of the driver (16), wherein the first subsection (20.1) is arranged in a central region (Q) of the driver (16), wherein the second subsection (20.2) extends from a lateral surface (24) of the driver (16) to the central region (Q) of the driver (16).

5. Driver (16) according to Claim 4, wherein the first subsection (20.1) has a second extent (L2) in the second direction (Y), wherein the second subsection (20.2) has a third extent (L3) in the longitudinal direction (X), wherein the second extent (L2) and / or the third extent (L3) each lie in a range from 1.0 to 1.25 times or in the range from 1.0 to 1.15 times a diameter (D) of the cable (14.1).

6. Driver (16) according to one of the preceding claims, wherein the opening (17) formed by the first and second inner contours (17.1, 17.2) has an arcuate or angled profile in a cross-sectional plane (S1) which runs parallel to a longitudinal extent of the driver (16) and perpendicularly to a base area (G) of the driver (16).

7. Driver (16) according to one of the preceding claims, wherein the cutout (16.4') is designed in such a manner that, when the closure element (16.4) is released from the complementary part (C), the cable (14.1) can be placed into the driver (16) in a second direction (Y) which runs perpendicularly to a longitudinal extent of the driver (16) and parallel to a base area (G) of the driver (16).

8. Driver (16) according to one of the preceding claims, wherein the closure element (16.4) is designed to relieve tension on the cable (14.1) in the connected state.

9. Driver (16) according to one of the preceding claims, wherein the driver (16) has a mounting region (16.1) for connecting the driver (16) to an object (2) to be measured, wherein the driver (16) is designed in such a manner that the cable (14.1) can be guided through the mounting region (16.1) in a longitudinal section (L) of the driver (16) in a longitudinal direction (X) which runs parallel to a longitudinal extent of the driver (16).

10. Driver (16) according to one of the preceding claims, wherein the opening (17) has a round, square or rectangular cross section.

11. Driver (16) according to one of the preceding claims, wherein the opening (17) has a fourth extent (L4) in a plane (S2) which runs parallel to a base area (G) of the driver (16), wherein the fourth extent (L4) lies in a range from 1.0 to 1.25 times or in the range from 1.0 to 1.15 times a diameter (D) of the cable (14.1).

12. Driver (16) according to Claim 11, wherein the fourth extent (L4) lies in a range from 2 mm to 20 mm or in the range from 5 mm to 15 mm.

13. Position measuring device with a driver (16) according to one of the preceding claims, wherein the position measuring device is an encapsulated length measuring device with a single-part or two-part housing.