Position measuring device

Abstract

Position measuring device with a scale (100) and a scanning unit (200) movable relative to it, wherein the scale (100) is arranged in an interior space (6.1, 6.2, 6.3) formed by a housing (1.1, 1.2), and wherein at least a part of this interior space (6.1, 6.2, 6.3) of the housing (1.1, 1.2) can be pressurized, for which purpose an air inlet opening (7.1, 7.2, 7.3) with a throttle element (8.1, 8.2, 8.3) is provided on the housing (1.1, 1.2), characterized by the fact the throttling element (8.1, 8.2, 8.3) a constriction (9.1, 9.2, 9.3) of the flow cross-section (A) less than 1 mm 2 exhibits, and This throttle element (8.1, 8.2, 8.3) is located downstream of the air inlet opening (7.1, 7.2, 7.3).

Description

AREA OF TECHNOLOGY

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

[0002] To measure the relative position of two machine parts, a scale is attached to one of the machine parts, and a scanning unit is attached to the other of the movable parts. During position measurement, the scale is scanned by the scanning unit, and position-dependent scanning signals are generated.

[0003] The scale is protected within an externally sealed interior space, which is at least partially pressurized to increase the sealing effect.

[0004] According to the generic patent DE 43 09 648 A1, the scale and scanning unit are arranged together within a housing. The interior of the housing is pressurized. For this purpose, an air inlet opening is provided on the housing, into which a throttle element is screwed from the outside.

[0005] Typically, the throttle element suitable for the position measuring device is provided to the customer as an accessory by the device manufacturer, and the customer must screw it on before commissioning the device. The problem here is that the customer often forgets to screw it on, resulting in excessively high pressure inside the position measuring device during operation. This leads to very high compressed air consumption and can also create a suction effect, drawing in contaminated ambient air. Furthermore, the throttle elements available as accessories are usually turned metal parts, which are relatively expensive.

[0006] DE 10 2012 203 193 A1 discloses a position measuring device in which an air inlet opening is provided at the end of the housing, to which compressed air can be connected, thereby generating overpressure inside the housing. The end is designed such that the introduced compressed air strikes an impact surface and is deflected towards the sealing lips that seal the housing. Here, too, the compressed air supplied for proper operation must be throttled by a throttling element that can be screwed onto the outside of the end.

[0007] In the position measuring device according to DE 17 73 403 A, the interior containing the scale and the scanning unit is sealed to the outside by means of roof-shaped sealing lips. The interior thus formed is subdivided by means of further sealing lips, and compressed air is blown into the interior enclosed by the two pairs of roof-shaped sealing lips through a bore in the housing. SUMMARY OF THE INVENTION

[0008] The object of the invention is to provide a position measuring device with which proper measuring operation without disruptive influences is ensured.

[0009] This problem is solved by the position measuring device specified in claim 1.

[0010] This position measuring device comprises a scale and a scanning unit that is movable relative to it, wherein the scale is arranged in an interior formed by a housing, and wherein at least a part of this interior of the housing can be pressurized, for which purpose an air inlet opening with a throttle element is provided on the housing. The throttle element has a constriction of the flow cross-section of less than 1 mm. 2 and is located downstream of the air intake opening. Downstream means that the throttle element is located inside the air intake opening or in the interior of the housing.

[0011] In particular, the throttling element has a narrowing of the flow cross-section of 0.4 mm. 2 ± 0.1 mm 2 on.

[0012] The narrowing of the flow cross-section can be formed by several openings or by a single opening in the throttling element.

[0013] It is advantageous if the throttling element is made of plastic, in particular if it is a plastic injection-molded part.

[0014] Another embodiment consists in a baffle surface being arranged at a distance from the end of the narrowing of the flow cross-section, the baffle surface being preferably arranged at a distance of less than 2.0 mm from the end of the narrowing of the flow cross-section.

[0015] In particular, the throttling element is positively engaged with an inner wall of the housing facing into the interior. The positive engagement is designed to secure the throttling element against the force of the incoming air.

[0016] The positive fit can be achieved by pressing the throttling element against an inner wall of the housing using a plate. For example, the plate is clamped between the end face of a hollow profile and a housing cover, and the impact surface is formed by the plate.

[0017] The positive locking mechanism can also be achieved by holding the throttle element in an undercut, which, for example, forms a longitudinal guide for the throttle element that runs perpendicular to the force of the incoming air.

[0018] If the throttle element is made of plastic, especially if it is a plastic injection-molded part, the impact surface can be integrally molded onto it.

[0019] If the housing comprises a hollow profile which is closed at one end face with a cover, and the throttling element is arranged on an inner wall of the cover facing into the interior, the throttling element is advantageously held in a form-fitting manner between the end face of the hollow profile and the cover.

[0020] If the housing includes a hollow profile that has a slot extending in the longitudinal direction of the scale, which is covered by a seal, and the narrowing of the flow cross-section directs the airflow in this longitudinal direction, it is advantageous if the baffle surface of the throttle element deflects this airflow by at least approximately 90° in the direction of the slot.

[0021] To direct the airflow, the throttle element has an air outlet opening that points exclusively in the direction of the slot.

[0022] The position measuring device designed according to the invention has the advantage that contamination of the interior of the position measuring device can be largely avoided. The invention ensures, on the one hand, that a sufficient quantity of air is supplied to maintain overpressure, and on the other hand, that the quantity of air supplied to the interior of the position measuring device is limited to a permissible level. At an applied pressure of 1 ± 0.2 bar, the supplied volume of air is limited to approximately 7 to 10 l / min.

[0023] By arranging the throttle element downstream of the air inlet opening or inside the position measuring device, manipulation of the throttle element by the user of the position measuring device is at least largely prevented.

[0024] Further details and advantages of the present invention will be explained with reference to the following description of exemplary embodiments in conjunction with the figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] It shows Fig. 1 a longitudinal section of a first position measuring device according to the invention; Fig. 2 the area of ​​the throttle element Fig. 1 shown enlarged; Fig. 3 an exploded view of the area of ​​the throttle element made of Fig. 1 and Fig. 2; Fig. 4 a longitudinal section of a second position measuring device designed according to the invention; Fig. 5 the area of ​​the throttle element from Fig. 4 shown enlarged; Fig. 6 a view A of the throttle element according to Fig. 5; Fig. 7 a perspective view of the throttle element according to the second embodiment with a view of the air outlet opening; Fig. 8 a cut BB through the in Fig. 7 Throttle element shown with a view of the air inlet opening; Fig. 9 a cross-section through an end piece of a third position measuring device; Fig. 10 a perspective view of the throttle element according to Fig. 9, and Fig. 11 a cut CC through the in Fig. 10 throttle elements shown. DESCRIPTION OF THE EXECUTION FORMS

[0026] The invention is explained in detail with reference to several exemplary embodiments. Each of these embodiments is a photoelectric length measuring device consisting of the basic components scale 100 and scanning unit 200, which are movable relative to each other in the measuring direction X. During measurement operation, the scanning unit 200 scans a measuring division 101 of the scale 100 and generates position measurements from the scanning signals. The scanning unit 200 is connected via a driver 300 to an object to be measured, whose position relative to the scale 100 is to be measured.

[0027] The reference symbols for the components scale 100, measuring division 101, scanning unit 200 and driver 300 are used in all subsequent embodiments.

[0028] The first embodiment of the invention is described by reference to the Fig. 1, Fig. 2 to Fig. 3 further explained. The scale 100 is protected within a housing 1.1. For this purpose, the housing 1.1 comprises a hollow profile 2.1 elongated in the measuring direction X, which is closed at both ends by a cover 3.1. The hollow profile 2.1 has a slot 13.1 extending in the measuring direction X, through which the driver 300 of the scanning unit 200 engages in a known manner. The slot 13.1 is covered by a seal 4.1, which seals an interior 6.1 of the housing 1.1 to the outside. The seal 4.1 is preferably designed in the form of a pair of sealing lips through which the driver 300 extends.

[0029] The housing 1.1, consisting of the hollow profile 2.1, the cover 3.1 at one end and another cover at the other end, and the outer seal 4.1, encloses the interior space 6.1. This interior space 6.1, or a part of it, is pressurized in such a way that ambient media cannot enter the interior space 6.1.

[0030] In the first embodiment, the interior space 6.1 is divided by an additional inner seal 5. This space enclosed by the two seals 4.1 and 5, as part of the interior space 6.1, is pressurized.

[0031] To generate overpressure, an air inlet opening 7.1 is provided on the cover 3.1, to which a compressed air line (not shown) can be connected from the outside. Downstream of the air inlet opening 7.1, i.e., starting from the air inlet opening 7.1, a throttling element 8.1 is arranged in the interior 6.1, which constricts 9.1 the flow cross-section A by less than 1 mm. 2 exhibits, in particular a narrowing 9.1 of the flow cross-section A of 0.4 mm 2 ± 0.1 mm 2 exhibits.

[0032] The constriction 9.1 of the flow cross-section A from the air inlet opening 7.1 is preferably formed by a single opening in the throttle element 8.1. Alternatively, the required constriction 9.1 of the flow cross-section A can also be formed by several openings; the essential point is that the resulting flow cross-section A is less than 1 mm². 2 , especially to 0.4 mm 2 ± 0.1 mm 2The throttle element 8.1 is made of plastic and is preferably an injection-molded part made of a thermoplastic. It is installed and positioned from the inside in a recess of the cover 3.1 and thus of the housing 1.1. The throttle element 8.1 is sealed against the cover 3.1 by means of a seal 17.1.

[0033] To deflect the airflow coming through the flow cross-section A and to calm the introduced airflow, a baffle surface 10.1 is provided. The baffle surface 10.1 is arranged at a distance H < 2.0 mm from the end of the constriction 9.1 of the flow cross-section A. From the baffle surface 10.1, the incoming air is deflected into the interior space 6.1, in the exemplary embodiment into the part of the interior space 6.1 separated by the inner seal 5.

[0034] In the first embodiment, the impact surface 10.1 is formed by a plate 11. This plate 11 holds the throttling element 8.1 in a form-fitting and captive position on the cover 3.1. The plate 11 is in turn pressed against the end face of the hollow profile 2.1 by means of the cover 3.1, the cover 3.1 being screwed onto the hollow profile 2.1.

[0035] Optionally, a cone-shaped elevation 12.1 is arranged centrally to the flow cross-section A at the impact surface 10.1. This elevation 12.1 serves to deflect the incoming air with minimal turbulence.

[0036] Any liquids and particles present in the incoming airflow are deposited at the impact surface 10.1, preventing them from reaching the scale of 100. Fine oil droplets contained in the incoming air are deposited, and at least some of these flow in a controlled manner along the impact surface 10.1 into a collection chamber 16.1, which acts as a separator. In the first embodiment, this collection chamber 16.1 is bounded by a wall of the plate 11 and a wall of the cover 3.1, as well as a seal inserted between these two walls. It is assumed that the position measuring device is mounted on an object to be measured (machine part) as shown in the Fig. As shown in Figure 1, the outer seal 4.1 and the slot 13.1 are facing downwards. In this installation position, the collection chamber 16.1 is lower than an air outlet opening 14.1 that points into the interior 6.1.

[0037] The air outlet opening 14.1 has a larger cross-section than the flow cross-section A of the constriction 9.1 of the throttle element 8.1. The air outlet opening 14.1 projects into a portion of the interior space 6.1, which is sealed off to the outside by the outer seal 4.1 and which is sealed off from the rest of the interior space – which has a scale of 100 – by an inner seal 5. The seals 4.1 and 5 preferably each consist of a pair of sealing lips through which the driver 300 passes in a known manner.

[0038] The arrangement of the throttle element 8.1 downstream of the air inlet opening 7.1 in the interior 6.1 of the housing 1.1 has the advantage that it can be optimized by the manufacturer of the position measuring device and can be safely positioned; furthermore, manipulation by the user of the position measuring device is at least largely prevented.

[0039] Based on the Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig. Section 8 describes a second embodiment of the invention. Fig. Figure 4 shows a longitudinal section of the second position measuring device designed according to the invention, Fig. 5 the area of ​​the throttle element from Fig. 4 shown enlarged and Fig. 6 a view A of the throttle element according to Fig. 5. Fig. 5 is a partial section DD of the Fig. 6. According to the first embodiment, the scale 100 is protected within the housing 1.2 and is scanned by the scanning unit 200 during position measurement. The longitudinal slot 13.2 of the hollow profile 2.2 is sealed by means of the seal 4.2, through which the driver 300 of the scanning unit 200 passes. A throttle element 8.2 is arranged on the end cap 3.2.

[0040] To generate overpressure in the interior 6.2, an air inlet opening 7.2 is provided on the cover 3.2, to which a hose (not shown) can be connected from the outside. Starting from the air inlet opening 7.2, the throttle element 8.2 is arranged in the interior 6.2 of the housing 1.2, which creates a constriction 9.2 of the flow cross-section A of less than 1 mm. 2 exhibits, in particular a narrowing 9.2 of the flow cross-section A of 0.4 mm 2 ± 0.1 mm 2 .

[0041] The constriction 9.2 of the flow cross-section A from the air inlet opening 7.2 is formed by a single opening in the throttle element 8.2. The throttle element 8.2 is made of plastic and is installed and positioned from the inside in a recess of the cover 3.2 and thus of the housing 1.2. The throttle element 8.2 is held in position on the inner wall of the cover 3.2 by mechanical positive locking, as it is pressed and clamped against the end face of the hollow profile 2.2 by the cover 3.2, as shown in the Fig. 6 can be seen. In addition, the throttle element 8.2 can be secured to the cover 3.2 by adhesive bonding, whereby the adhesive bonding also provides a seal between the cover 3.2 and the throttle element 8.2.

[0042] In contrast to the first embodiment, a baffle surface 10.2 is integrally formed with the throttling element 8.2. The throttling element 8.2 with the baffle surface 10.2 integrally formed with it is a plastic injection-molded part. The baffle surface 10.2 is located at a distance H < 2.0 mm from the end of the constriction 9.2 of the flow cross-section A.

[0043] The incoming air is deflected from the baffle surface 10.2 towards the seal 4.2 and into the interior space 6.2. This deflection occurs in several stages. To deflect the incoming air, the baffle surface 10.2 runs at least largely perpendicular to the constriction 9.2 (flow opening), deflecting the incoming air by approximately 90°. A further surface is arranged on the throttle element 8.2, designed to deflect this already redirected air again, this time towards the seal 4.2. One wall of the throttle element 8.2 faces the seal 4.2 and thus the slot 13.2. This wall has structures 15.2 and 15.3 designed and arranged for directed airflow. The structures 15.2 extending towards the slot 13.2 are designed as grooves or ribs. As seal 4.2, preferably a pair of sealing lips is provided through which the driver 300 passes.

[0044] The throttle element 8.2 has an air outlet opening 14.2, which directs the airflow towards the slot 13.2. Air outlet in other directions is prevented by an upper wall and two lateral baffles on the throttle element 8.2. The upper wall and the lateral baffles are integrally formed on the throttle element.

[0045] The Fig. 9, Fig. 10 to Fig. Figure 11 shows a third embodiment of the invention. To avoid repetition, the housing of the length measuring device is not shown in its entirety. To generate the overpressure, an air inlet opening 7.3 is provided on the cover 3.3, to which a hose (not shown) can be connected from the outside. Starting from the air inlet opening 7.3, the throttle element 8.3 is arranged in the interior 6.3 of the housing, which creates a constriction 9.3 of the flow cross-section A of less than 1 mm. 2exhibits, in particular a narrowing 9.3 of the flow cross-section A of 0.4 mm 2 ± 0.1 mm 2 .

[0046] The constriction 9.3 of the flow cross-section A from the air inlet opening 7.3 is formed by a single opening in the throttle element 8.3. The throttle element 8.3 is made of plastic and is installed in a recess of the cover 3.3, and thus of the housing, from the inside and is positively engaged, with the positive engagement acting against the force of the flow acting on the constriction 9.3.

[0047] The baffle surface 10.3 is integrally molded onto the throttle element 8.3. The throttle element 8.3, with the baffle surface 10.3 molded onto it, is an injection-molded plastic part. The baffle surface 10.3 is located at a distance H < 2.0 mm from the end of the constriction 9.3 of the flow cross-section A. The incoming air is deflected by the baffle surface 9.3 towards the seal in the interior space 6.3.

[0048] The impact surface 10.3 is formed by an inner wall of the throttle element 8.3, located downstream of and opposite the constriction 9.3. This wall of the throttle element 8.3 comprises structures 15.3 extending towards the seal and thus the slot, in the form of grooves or ribs. These structures 15.3 serve to direct the airflow towards the slot.

[0049] The throttling element 8.3 is designed and arranged such that the air deflected at the impact surface 10.3 flows exclusively in the direction of the seal; for this purpose, the air outlet opening 14.3 points in this direction into the interior 6.3. The seal is preferably designed as a pair of sealing lips.

[0050] In accordance with the first embodiment described above, a conical or cutting-edge raised section 12.3 can also be provided to fan out the air at the impact surface 10.3.

[0051] To ensure that air enters the interior 6.3 only through the constriction 9.3, the throttle element 8.3 is bonded to the cover 3.3. Secure positioning is further guaranteed by a positive fit with the cover 3.3. This positive fit is achieved by holding the throttle element 8.3 in an undercut that forms a longitudinal guide for the throttle element 8.3, running perpendicular to the force exerted by the incoming air.

[0052] The invention can be successfully used with all physical scanning principles. The measuring scale can be designed to be optically, magnetically, inductively, or capacitively scanned.

[0053] In the exemplary embodiments, the invention is explained using linear measuring devices, but the invention is not limited to this; it can also be used with angle measuring devices.

Claims

[1] Position measuring device with a scale (100) and a scanning unit (200) that is movable relative to it, wherein the scale (100) is arranged in an interior space (6.1, 6.2, 6.3) formed by a housing (1.1, 1.2), and wherein at least a part of this interior space (6.1, 6.2, 6.3) of the housing (1.1, 1.2) can be pressurized, for which purpose an air inlet opening (7.1, 7.2, 7.3) with a throttle element (8.1, 8.2, 8.3) is provided on the housing (1.1, 1.2), characterized by that the throttling element (8.1, 8.2, 8.3) a constriction (9.1, 9.2, 9.3) of the flow cross-section (A) less than 1 mm 2 exhibits, and This throttle element (8.1, 8.2, 8.3) is located downstream of the air inlet opening (7.1, 7.2, 7.3). [2] Position measuring device according to claim 1, wherein the throttling element (8.1, 8.2, 8.3) has a constriction (9.1, 9.2, 9.3) of the flow cross-section (A) of 0.4 mm 2 ± 0.1 mm 2 exhibits. [3] Position measuring device according to one of the preceding claims, wherein the narrowing (9.1, 9.2, 9.3) of the flow cross-section (A) is formed by a single opening in the throttling element (8.1, 8.2, 8.3). [4] Position measuring device according to one of the preceding claims, wherein the throttle element (8.1, 8.2, 8.3) is positively engaged with the housing (1.1, 1.2). [5] Position measuring device according to one of the preceding claims, wherein the throttle element (8.1, 8.2, 8.3) is made of plastic. [6] Position measuring device according to one of the preceding claims, wherein a baffle surface (10.1, 10.2, 10.3) is arranged spaced apart from the end of the constriction (9.1, 9.2, 9.3) of the flow cross-section (A). [7] Position measuring device according to claim 6, wherein the impact surface (10.1, 10.2, 10.3) is arranged at a distance (H) less than 2.0 mm from the end of the constriction (9.1, 9.2, 9.3) of the flow cross-section (A). [8] Position measuring device according to claim 6 or 7, wherein the housing (1.1) comprises a hollow profile (2.1) which is closed at an end face with a cover (3.1), and wherein the throttle element (8.1) is arranged on an inner wall of the cover (3.1) facing into the interior (6.1) and is pressed against this inner wall by means of a plate (11) by clamping the plate (11) between the end face of the hollow profile (2.1) and the cover (3.1), and wherein the impact surface (10.1) is formed by the plate (11). [9] Position measuring device according to claim 8, wherein the plate (11) comprises at least one air outlet opening (14.1) into the interior (6.1), and wherein the cross-section of the air outlet opening (14.1) is larger than the flow cross-section (A) of the constriction (9.1) of the throttle element (8.1). [10] Position measuring device according to claim 9, wherein the air outlet opening (14.1) projects into a part of the interior (6.1) which is closed off to the outside by an outer seal (4.1) and which is closed off from the rest of the interior (6.1) which has the scale (100) by an inner seal (5). [11] Position measuring device according to claim 6 or 7, wherein the throttle element (8.2, 8.3) is made of plastic and the impact surface (10.2, 10.3) is integrally formed on it. [12] Position measuring device according to claim 11, wherein the housing (1.2) comprises a hollow profile (2.2) which is closed at an end face with a cover (3.2), and wherein the throttle element (8.2) is arranged on an inner wall of the cover (3.2) facing into the interior (6.2) and the throttle element (8.2) is clamped between the end face of the hollow profile (2.2) and the cover (3.2). [13] Position measuring device according to one of the preceding claims 11 to 12, wherein the housing (1.2) comprises a hollow profile (2.2) having a slot (13.2) extending in the longitudinal direction of the scale (100), which is covered by a seal (4.2), and wherein the constriction (9.2, 9.3) of the flow cross-section (A) directs the airflow in this longitudinal direction, and the baffle surface (10.2, 10.3) of the throttle element (8.2, 8.3) deflects this airflow. [14] Position measuring device according to claim 13, wherein the throttle element (8.2, 8.3) has an air outlet opening (14.2, 14.3) pointing exclusively in the direction of the slot (13.2) for the directed guidance of the airflow. [15] Position measuring device according to claim 13 or 14, wherein the throttle element (8.2, 8.3) comprises a surface downstream of the air outlet opening (14.2, 14.3) which has structures (15.2, 15.3) designed and arranged for directed air guidance.

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