Measuring device with a dustproof element

Abstract

Measuring device comprising a first dustproof element (4) and a second dustproof element (4) provided on a frame (1) of the measuring device to cover an insertion opening (1a) of the frame (1) of the measuring device, wherein the measuring device includes the frame (1) in which a scale (2) is held and the insertion opening (1a) is formed in a longitudinal direction of the scale (2), and a detector (3) which can be inserted through the insertion opening (1a) and is able to move along the insertion opening (1a) in the longitudinal direction to obtain position information from the scale (2), wherein each of the first and second dustproof elements (4) is characterized in that it comprises: a base section (4a), a tongue section (4b), a projecting section (4c), and at least one reinforcing element (4d) extending continuously in the longitudinal direction and arranged in a lateral direction in a substantially central region of the dustproof element (4), wherein the projecting section (4c) is formed such that it extends substantially over the entirety of the tongue section (4b) in the longitudinal direction, wherein the projecting section (4c) protrudes from a surface of the tongue section (4b) at a position near the tip of the tongue section (4b), and wherein, when the detector (3) is not inserted through the insertion opening (1a) of the measuring device, the surface of the tongue section (4b) at the position near the tip of the tongue section (4b) of the first dustproof member (4) comes into contact with the second dustproof member (4) which faces the tongue section (4b) of the first dustproof member (4), and tip sections of the dustproof members (4) are brought into engagement due to the projecting sections (4c) of the dustproof members (4) and the dustproof members (4) are held in a distorted state in order to close the insertion opening (1a) of the frame (1).

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The present invention relates to a measuring device with a dustproof element. 2. Description of the related technology

[0002] A linear encoder mounted in a machine tool or similar device is an example of a measuring device. First, a general structure of a linear encoder is described. Fig. Figure 1 is a schematic diagram representing a general linear encoder. Fig. Figure 5 is a sectional view of the general linear encoder. For simplicity, in the following description, the longitudinal direction, transverse direction, and thickness direction of a scale contained in the linear encoder are sometimes referred to as the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively.

[0003] As it is in Fig. 1 and Fig. As shown in Figure 5, in a general linear encoder, a scale 2 is held in a frame 1, and an insertion aperture 1a is formed in the frame 1 such that it extends in the X-axis direction. The scale 2 and a detector 3 are moved relative to each other while the detector 3 is inserted through the insertion aperture 1a, and the detector 3 receives position information from the scale 2 (see, for example, JP 2008-267989A).

[0004] JP H01-267 415 A describes a sealing device for a displacement detector, which is installed in an optical displacement detector 1 and arranged between a table and a bed of a machine tool. The sealing device for the displacement detector is provided with a hollow housing, a connecting rod, and synthetic resin lip elements produced by casting a wire.

[0005] DE 41 01 579 A1 describes a position measuring device with a housing featuring a longitudinal slot, which is sealed by means of sealing lips. The sealing lips are made of elastic plastic. To prevent the sealing lips from stretching during assembly and long-term operation, they have a tensile-resistant thread or wire embedded in the base of the sealing lip.

[0006] US 3 330 567 A describes oil seals and an improved design for internally reinforced neck seals, as used in wet or dry rolling mills.

[0007] DE 29 32 389 C2 describes a measuring unit for determining the relative position of two movable objects. It uses a measuring scale on a support element on one of the objects and a reading plate on a reading head on the other object. An elastic strip 2 is positioned between the scale 3 and its support element 1. It does not lose its strength under the influence of changing ambient temperatures. The connection between the reading head 10 and its mount consists of an elastic strip 12, which allows movement of the head 10 without affecting the parallelism between the center plane of the head and that of its mount.

[0008] DE 36 23 353 A1 describes an encapsulated measuring device in which the cover elements, arranged on both sides of a longitudinal slot in a pre-chamber of the hollow profile, have a comb-like cross-section, forming a labyrinth in the area of ​​their mutual sealing contact. The driver, which establishes the connection between the interior of the hollow profile and the environment, is meandering in shape, so that it follows the course of the labyrinth. In this way, the sealing capability is maintained even at the point where the driver penetrates the profile.

[0009] DE 34 10 944 C1 describes an encapsulated measuring system with a driver connected to a scanning unit that extends through a slot in a housing of the measuring system. This slot is sealed against lubricants and coolants by a pair of multi-part sealing elements. Each multi-part sealing element comprises a proprietary sealing profile and a support element. The sealing profiles perform the sealing function, while the support elements provide the necessary permanent elasticity and dimensional stability. Because of this division of tasks, the sealing profiles themselves can be made of materials resistant to aggressive media such as lubricants and coolants, but which, on their own, do not possess sufficient elasticity or dimensional stability to be used independently.

[0010] The JP S63 - 120 107 U describes a measuring unit for determining the relative position of two objects.

[0011] DE 32 15 336 C1 describes an encapsulated measuring device for measuring the relative position of two objects. The measuring device comprises a pair of sealing lips, each attached to an edge of a housing for the measuring device, and together covering an opening in the housing. The lips define areas of greater flexibility adjacent to areas of less flexibility. A driver passes through the opening between the sealing lips.

[0012] To prevent oil, dust (including machine dust), etc., from entering the frame 1 through the insertion opening 1a, the frame 1 in this structure is provided with dustproof elements 101 arranged so that they face each other across the insertion opening 1a in the Z-axis direction. When the scale 2 and the detector 3 are moved relative to each other, the detector 3 moves along the insertion opening 1a of the frame 1 in the X-axis direction, while pushing the opposing dustproof elements 101 to the side.

[0013] Now the structure of each dustproof link 101 is described. Fig. Figure 6 represents a structure of a general dustproof element 101. The length of the dustproof element 101 in its longitudinal direction is essentially equal to the length of the insertion opening 1a of the frame 1 in the X-axis direction. The dustproof element 101 comprises a base section 101a, which fits into a fitting recess 1b of the frame 1, and a tongue section 101b, which projects from the base section 101a.

[0014] The dustproof element 101 generally consists of a flexible material, such as urethane, and incorporates a wire 102 made of a metal or synthetic fiber to prevent longitudinal expansion or elongation of the dustproof element 101 due to, for example, absorption of cutting oil or the like. The wire 102 is located near the tip section of the dustproof element 101.

[0015] Since the wire 102 is positioned near the tip section of the dustproof element 101, as described above, the wire 102 of the dustproof element 101 is deformed when, for example, the detector 3 moves along the insertion opening 1a of the frame 1. If the detector 3 moves repeatedly, the wire 102 is deformed repeatedly. Therefore, the tip section of the dustproof element 101 eventually becomes deformed so that it cannot return to its original shape, and the quality of the seal between the dustproof element 101 and the detector 3 deteriorates. SUMMARY OF THE INVENTION

[0016] The present invention was created to solve the problems described above, and it is an object of the present invention to provide a measuring device which includes a dustproof element with which deformation due to movement of a detector can be prevented.

[0017] The object of the present invention is achieved by the subject matter of independent claim 1. Further embodiments are defined in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic perspective view of a general linear encoder. Fig. Figure 2 is a schematic sectional view of a dustproof element according to one embodiment. Fig. Figure 3 is a schematic sectional view showing how dustproof elements according to the embodiment cover an insertion opening of a frame in a region where a detector is not inserted through the insertion opening. Fig. Figure 4 is a schematic sectional view showing how the dustproof elements according to the embodiment cover the insertion opening of the frame in a region where a detector is inserted through the insertion opening. Fig. Figure 5 is a schematic sectional view of a general linear encoder. Fig. Figure 6 is a schematic sectional view of a general dustproof element. DESCRIPTION OF PREFERRED EXECUTION FORMS

[0018] One embodiment of the present invention will now be described with reference to the drawings. However, the present invention is not limited to this embodiment. For ease of understanding, the following description and the drawings have been simplified as appropriate.

[0019] First, the basic structure of a measuring device is described, in which dust-tight elements of the present embodiment are integrated. The dust-tight elements of the present embodiment are integrated into a linear encoder, which is a typical example of a measuring device. The dust-tight elements of the present embodiment can also be integrated into a measuring device other than the linear encoder.

[0020] Although a structure of a linear encoder was described above in the Background of the Invention section, it will be briefly summarized again with reference to Fig. 1 and Fig. 5 described. According to the representation in Fig. 1 and Fig. In a general linear encoder, a scale 2 is held in a frame 1, and an insertion aperture 1a is formed in the frame 1 such that it extends in the X-axis direction. The scale 2 and the detector 3 are moved relative to each other while the detector 3 is inserted through the insertion aperture 1a, and the detector 3 receives position information from the scale 2.

[0021] To prevent dust and the like from entering the frame 1 through the insertion opening 1a, a dustproof element is required in this structure as described above. The dustproof elements of the present embodiment are integrated into the dustproof structure.

[0022] Scale 2 can be, for example, an optical scale or an electromagnetic induction scale for a general linear encoder. Detector 3 is configured to receive position information from scale 2.

[0023] The structure of the dustproof elements according to the present embodiment will now be described. Fig. Figure 2 shows the structure of each dustproof element 4. The dustproof element 4 comprises a base section 4a, a tongue section 4b, a projecting section 4c, and a reinforcing element 4d. The base section 4a, the tongue section 4b, and the projecting section 4c are integrally formed from a flexible material such as urethane, nitrile rubber, nitrile butadiene rubber (NBR), or fluorocarbon rubber, such that the reinforcing element 4d is arranged therein.

[0024] The longitudinal length of the base section 4a is essentially equal to the length of the insertion opening 1a of the frame 1 in the X-axis direction. The base section 4a is formed in a shape corresponding to the shape of the fitting recesses 1b formed in the frame 1 and is fitted into the corresponding fitting recess 1b of the frame 1. The shape of the base section 4a is not specifically restricted as long as the dustproof element 4 can be supported, carried, or mounted by the corresponding fitting recess 1b of the frame 1.

[0025] According to the representation in Fig. 3 and Fig. 4. The fitting recesses 1b of the frame 1 are arranged such that they face each other in the Z-axis direction via the insertion opening 1a of the frame 1. Each fitting recess 1b, viewed in the X-axis direction, has a substantially rectangular shape and an opening 1c facing the insertion opening 1a. The shape of the fitting recess 1b is not restricted as long as the base section 4a of the dustproof links 4 can be properly fitted into the fitting recesses 1b.

[0026] The opening 1c of each fitting recess 1b in the frame 1 is partially covered by a side wall 1d that projects in the positive Y-axis direction from the fitting recess 1b at a position near the insertion opening 1a. The side wall 1d is preferably curved at its apex to avoid damaging the corresponding dustproof element 4, even if the dustproof element 4 comes into contact with it.

[0027] With respect to each dustproof member 4, the tongue section 4b is formed such that it extends over substantially the entirety of the base section 4a in the longitudinal direction and is a plate-shaped member projecting from the base section 4a. The length of the tongue section 4b in the transverse direction (latitudinal direction), which is described in detail below, is determined such that the insertion opening 1a of the frame 1 can be reliably covered by the opposing dustproof members 4.

[0028] The projecting section 4c is designed to extend over substantially the entirety of the tongue section 4b in the longitudinal direction. The projecting section 4c, which is described in detail below, extends from a surface of the tongue section 4b at a position near the tip of the tongue section 4b, with the surface coming into contact with the dustproof element 4 facing the tongue section 4b. The function of the projecting section 4c is described below.

[0029] The reinforcing element 4d reinforces the dustproof element 4. The reinforcing element 4d is preferably a wire made of metal or synthetic fiber, such as aramid. In particular, the reinforcing element 4d is preferably a stranded wire made of metal or synthetic fiber, such as aramid. In such a case, the adhesion between the material of the reinforcing element 4d and the flexible material can be increased when they are integrated together.

[0030] The reinforcing element 4d extends over the entire length of the dustproof element 4 in the longitudinal direction. The reinforcing element 4d is positioned at least in a substantially central region of the dustproof element 4 in the lateral direction. More precisely, the reinforcing element 4d is arranged such that it is not easily deformed by movement of the detector 3 when the detector 3 is moved along the frame 1. Even with repeated movement of the detector 3 along the frame 1, deformation of the reinforcing element 4d is thus prevented. Consequently, deformation of the tip section of the dustproof element 4 due to movement of the detector 3 is prevented, and the quality of the seal between the dustproof element 4 and the detector 3 is improved.

[0031] Furthermore, both end sections of the dustproof element 4 exhibit essentially the same deformation characteristics in the lateral direction, and any difference, for example, in the amount of expansion in the longitudinal direction due to the absorption of cutting oil or the like between the two end sections of the dustproof element 4 in the lateral direction can be reduced. Consequently, twisting and distortion of the dustproof element 4 can be prevented.

[0032] In the case where the dustproof link 4 is manufactured by extrusion using fluorocarbon rubber, only one reinforcing element 4d needs to be placed in the dustproof link according to the manufacturing process. Compared to the case where a wire is placed in an end section of the dustproof link 4 in the lateral direction, the distance between the reinforcing element 4d and each end section of the dustproof link 4 in the lateral direction can be reduced in this case. Consequently, both end sections of the dustproof link 4 exhibit essentially the same deformation characteristics in the lateral direction, and twisting and distortion of the dustproof link 4 can be prevented.

[0033] Even if heat shrinkage occurs during the extrusion process, twisting and distortion of the dustproof member 4 can be prevented because both end sections of the dustproof member 4 have essentially the same deformation characteristics in the width direction.

[0034] The reinforcing element 4d can be located in a substantially central region of the dustproof element 4 along the width W of the dustproof element 4 or substantially at the centroid of the dustproof element 4 in the cross-section of the dustproof element 4.

[0035] The reinforcing element 4d is preferably arranged in a substantially central region of the dust-tight element 4 in the thickness direction. In the present embodiment, the reinforcing element 4d is arranged in a substantially central region of the tongue section 4b in the thickness direction, and a section around the reinforcing element 4d is made thicker. Thus, the reinforcing element 4d is reliably covered, and the possibility of the reinforcing element 4d being cut by machining dust or the like can be reduced.

[0036] An example in which the dustproof elements 4 of the present embodiment are installed in a dustproof structure of a linear encoder is now described. Fig. Figure 3 represents the way in which the opposing dustproof links 4 cover the insertion opening 1a of the frame 1 in a region where the detector 3 is not or will not be inserted. Fig. Figure 4 represents the way in which the opposing dustproof elements 4 cover the insertion opening 1a of the frame 1 in a region where the detector 3 is or will be inserted.

[0037] According to the representation in Fig. 3 and Fig. 4 The base sections 4a of the dustproof links 4 described above are fitted into the respective recesses 1b of the frame 1, so that the tongue sections 4b protrude onto the openings 1c of the recesses 1b.

[0038] In the region where the detector 3 is not inserted through the insertion opening 1a of the frame 1, the tip sections of the dustproof links 4, which are arranged so that they face each other in the Z-axis direction, contact each other in order to close the insertion opening 1a of the frame 1 in such a state that the dustproof links 4 are distorted or warped, that is, the tip section of each dustproof link 4 is deformed pivotably or rotatably in the negative Y-axis direction.

[0039] In the present embodiment, as it is in Fig. As shown in Figure 3, the tip sections of the dustproof links 4 are engaged by the projecting sections 4c of the dustproof links 4, and the dustproof links 4 are held in the deformed state. Consequently, each dustproof link 4 exerts a restoring force in one direction such that the other dustproof link 4 is pushed or pressed. Even if the tip section of one of the dustproof links 4 attempts to pivot or rotate in the negative Y-axis direction in order to change the state of the tip sections of the dustproof links 4 from the closed state to an open state, the dustproof link 4 is restrained by the restoring force. Therefore, it is possible to prevent dust or similar substances from penetrating the frame 1.

[0040] In the region where the detector 3 is inserted through the insertion opening 1a of the frame 1, the tip sections of the dustproof elements 4, which are arranged so that they face each other in the Z-axis direction, surround the detector 3 in a sandwich-like manner in order to close the insertion opening 1a of the frame 1 in such a state that the dustproof elements 4 are distorted or warped.

[0041] In the present embodiment, as it is in Fig.As shown in Figure 4, the projecting sections 4c of the dustproof elements 4 are in contact with the detector 3, and the dustproof elements 4 are held in the deformed state. Consequently, each dustproof element 4 exerts a restoring force in one direction such that the detector 3 is pushed or pressed. Even if the tip section of one of the dustproof elements 4 attempts to pivot or rotate in the negative Y-axis direction in order to change the state of the tip section of the dustproof element 4 and the detector 3 from the closed state to an open state, the dustproof element 4 is restrained by the restoring force. Therefore, it is prevented that dust or the like penetrates the frame 1.

[0042] Consequently, a dustproof element 4 is provided for a measuring device. The measuring device comprises a frame 1 in which a scale 2 is held and which has an insertion opening 1a extending in a longitudinal direction, and a detector which is inserted through the insertion opening 1a and is capable of moving along the insertion opening 1a in the longitudinal direction to obtain position information from the scale 2. The dustproof element 4 is provided on the frame 4 to cover the insertion opening 1a of the measuring device. The dustproof element 4 includes at least one reinforcing element 4d, which extends substantially continuously in the longitudinal direction and is arranged in a substantially central region of the dustproof element 4 in a lateral direction.The present invention is not limited to the embodiment described above and suitable modifications are possible within the scope of protection of the present invention.

Claims

[1] Measuring device comprising a first dustproof element (4) and a second dustproof element (4) provided on a frame (1) of the measuring device to cover an insertion opening (1a) of the frame (1) of the measuring device, the measuring device comprising the frame (1) in which a scale (2) is held and the insertion opening (1a) is formed in a longitudinal direction of the scale (2), and a detector (3) which can be inserted through the insertion opening (1a) and is able to move along the insertion opening (1a) in the longitudinal direction to obtain position information from the scale (2), each of the first and second dustproof elements (4) characterized by is that it includes: a base section (4a), a tongue section (4b), a projecting section (4c), and at least one reinforcing element (4d) extending continuously in the longitudinal direction and arranged in a lateral direction in a substantially central region of the dustproof element (4), wherein the projecting section (4c) is formed such that it extends substantially over the entirety of the tongue section (4b) in the longitudinal direction, wherein the projecting section (4c) protrudes from a surface of the tongue section (4b) at a position near the tip of the tongue section (4b), and wherein, when the detector (3) is not inserted through the insertion opening (1a) of the measuring device, the surface of the tongue section (4b) at the position near the tip of the tongue section (4b) of the first dustproof member (4) comes into contact with the second dustproof member (4) which faces the tongue section (4b) of the first dustproof member (4), and tip sections of the dustproof members (4) are brought into engagement due to the projecting sections (4c) of the dustproof members (4) and the dustproof members (4) are held in a distorted state in order to close the insertion opening (1a) of the frame (1). [2] Measuring device according to claim 1, wherein the amplifying element (4d) is arranged in a substantially central region along a width of the dustproof element (4). [3] Measuring device according to one of the preceding claims, wherein the reinforcing element (4d) is substantially arranged at a center of gravity of the dustproof element (4) in the cross-section of the dustproof element (4). [4] Measuring device according to one of the preceding claims, wherein the reinforcing element (4d) is arranged in a substantially central region in a thickness direction of the dustproof element (4). [5] Measuring device according to one of the preceding claims, wherein the reinforcing element (4d) is a stranded wire made of a metal or a synthetic fiber.

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