Holding mechanism and procedure

Abstract

A holding mechanism for a measuring device comprising a long scale frame (4) to be attached to a first measuring section (W1) and receiving a scale (5), and a detector (3; 7) to be attached to a second measuring section (W2) and arranged to be capable of displacement in a length direction of the scale frame (4), wherein the detector (3; 7) is configured to detect an amount of relative displacement with respect to the scale (5), the holding mechanism comprising: a first groove (14) formed in the scale frame (4) along the length direction of the scale frame (4); a second groove (15) formed in the detector (3; 7) such that it is substantially parallel to the first groove (14); and a pair of holders (20) configured to hold the detector (3; 7) by being attached to a first and a second side of the scale frame (4) in the length direction, wherein: each bracket (21, 22) of the pair of brackets (20) comprises: a main portion (30) to be mounted along a side surface of the scale frame (4) and the detector (3; 7); a first hook (40) projecting from the main portion (30) and adapted to engage the first groove (14); a second hook (50) projecting from the main portion (30) and adapted to engage the second groove (15); and a projection (60) projecting from the main portion (30) and positioned at a gap (16) between the scale frame (4) and the detector (3; 7), wherein the pair of holders (20) is displaceable from the first and second sides to the detector (3; 7) along the length direction of the scale frame (4), and each projection (60) can be inserted into the gap (16) between the scale frame (4) and the detector (3; 7), so that each projection (60) biases the scale frame (4) and the detector (3; 7) in different directions, wherein a thickness of each projection (60) is gradually thicker with increasing distance from the detector (3; 7).

Description

CROSS REFERENCE TO RELATED APPLICATIONSThis application claims priority to Japanese Application No. 2016-115755 filed on Jun. 9, 2016, the disclosure of which is expressly incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION1. Field of the InventionIn a measuring apparatus including a long scale frame housing and a detecting device that detects an amount of relative displacement to the scale, this invention relates to a holding mechanism and a holding method for holding the detecting device to the scale frame.2. DESCRIPTION OF THE RELATED ARTConventionally, there is known a measuring device (a linear scale) including a long scale frame housing accommodating a scale and a detecting device that detects an amount of relative displacement with respect to the scale, the measuring device measuring an amount of displacement between a pair of measurable portions (measurement portions) in a machine tool or the like. In such a measuring apparatus, a measuring apparatus main body is fixed to one of the two measuring portions while the detecting apparatus is fixed to the other of the two, and the detecting apparatus reads an amount of relative displacement from the scale in the scale frame, and thereby the measuring apparatus measures the amount of displacement between the measuring portions.In a measurement device in which the detection device is slidably disposed on the measurement device main body, for example, when the detection device moves in an arbitrary direction relative to the measurement device main body during a transportation step before being attached to the measurement portions, there is a possibility that the scale and the sensor of the detection device may collide and be damaged. In order to prevent such damage, a holding tool is used which holds the detection device on the measurement device main body and restricts the displacement. The holding tool is also used in attaching the measurement device to the measurement portions for positioning the detection device relative to the measurement device main body.A typical example of a holding tool holding the detection device includes a pair of holding members attached to both side surfaces in a displacement direction of the detection device, and the holding members are fixed to the scale frame by screwing. However, since the holding members are screwed in place, an operation of fastening and releasing the holding members may become complicated. In addition, in order to screw the holding members in place, a screw hole must be formed in the scale frame by tapping, and the time and cost involved can increase. Moreover, since the attachment position of the support members (i.e., a support position of the detection device) is limited by the screw hole, there is no freedom in positioning of the detection device when the detection device is attached to the measurement portions, and the ease of an attachment operation may decrease.In order to eliminate the above-mentioned disadvantages in conventional holding tools, there is proposed by these applicants a holding device including: a holder main body abutting against a side surface of a detection device; a holder extending from the holder main body and engaging with a groove of a scale frame; and a holder shifting device shifting the holder and engaging with the groove (see Japanese Patent JP 4 956 263 B2). According to the holder described in Japanese Patent JP 4 956 263 B2, by sliding the holder in a width direction of the groove using the holder sliding device and engaging the holder with the groove due to such a displacement, a detection device can be positioned at any position in a length direction of the scale frame, and ease of an operation of attaching the measurement device to a measurement portion can be improved.However, in the conventional holding device, the holder displacement device is configured by combining a plurality of different members such as threaded members, pressing members, biasing members, and the like, and therefore a structure of the holding device may become complicated. Further, since the holding member is engaged by rotating a threaded member from below the measurement device, the operations of fastening and releasing the holding device become complex, and the ease of the operation of fastening the measurement device cannot always be adequately achieved.Conventional fastening devices or holding mechanisms and measuring devices are described in JP H11-281 341 A and DE 39 17 717 A1. JP H11-281 341 A describes a head slider fixing device of a position detecting device for easily fixing a head slider to a main body at a low cost. To this end, a position detecting device is provided with a main body having a longitudinal recording medium and a slider movably mounted on the main body. A holder is provided with a main body side safety tab for engaging with the main body and a slider side safety tab for engaging with the slider. The holder is provided with a rectangular fixing part disposed between the fixing part and the slider. This fixing part is configured such that the main body side safety tab may be integrally formed at the end part on the main body side and the slider side safety tab may be integrally formed at the end part on the slider side. The fixing part is provided with an elastic displacement part provided in parallel in the moving direction of the slider between the main body side and the slider side safety tab, which elastically displaces in a direction orthogonally crossing the moving direction, and an operation member releasing the engagement state of the slider side safety tab.DE 39 17 717 A1 discloses a measuring device for monitoring relative displacements between a first component and a second component, comprising: an elongated graduation carrier provided with end pieces at both ends, two bearings fastened to the first component for receiving the end pieces, a hollow body receiving the graduation carrier, a measuring head axially displaceable on the graduation carrier for reading the graduation and for generating a corresponding read signal, and a driver connected to the second component, which driver is movable together with the measuring head, wherein at least one reference surface is formed on the outside of the hollow body for positioning the driver with respect to the end pieces.SUMMARY OF THE INVENTIONAccordingly, an object of this invention is to enable easy attachment and removal using a simple structure and to appropriately improve a process of attaching a measurement device. This object is achieved according to the invention by the features of the independent claims. Specific embodiments are the subject of the dependent claims.According to one aspect, there is provided a holding mechanism for use in a measurement apparatus including a long scale frame to be fixed to a first measurement portion and accommodating a scale, and a detection device (a detector) to be fixed to a second measurement portion and arranged to be displaceable in a length direction of the scale frame, the detection device configured to detect an amount of relative displacement with respect to the one scale, the holding mechanism comprising: a first groove formed in the scale frame along the length direction of the scale frame; a second groove formed in the detection device to be substantially parallel to the first groove; and a pair of holding devices (holders) configured to hold the detection device therethrough, being mounted on first and second sides of the scale frame in the length direction, wherein: each holder of the pair of holders comprises: a main portion for mounting along a side surface of the scale frame and the detector, a first hook projecting from the main portion and adapted to engage with the first groove, a second hook projecting from the main portion and adapted to engage with the second groove, and a projection projecting from the main portion and positioned at a gap between the scale frame and the detector, the two holders are slidable from the first and second sides along the length direction of the scale frame toward the detection direction, and each projection is insertable into the gap between the scale frame and the detector, such that each protrusion biases the scale frame and the sensing device in mutually different directions. Specifically, a holding mechanism is used in a measuring apparatus including a long scale frame fixed to a first measuring portion and accommodating a scale, and a detection device fixed to a second measuring portion and arranged to be displaceable in a length direction of the scale frame, the detection device detecting an amount of relative displacement with respect to the scale. The holding mechanism includes a first groove formed in the scale frame along the length direction of the scale frame, a second groove formed in the detection device so as to be parallel to the first groove, and a pair of holding members holding the detection device by being attached to the first and second sides in the length direction of the scale frame. The two holding members each include a substantially planar or plate-shaped main body (such as a specific main portion) mounted along a side surface of the scale frame and the detection device, a first hook portion projecting from the main body and engaging with the first groove, a second hook portion projecting from the main body and engaging with the second groove, and a projection projecting from the main body and positioned at a gap between the scale frame and the detection device. The two holding members are slid from the first and second sides toward the detection device along the length direction of the scale frame, and the protrusion is inserted into a gap between the scale frame and the detection device, and thereby the protrusion biases the scale frame and the detection device in different directions from each other.Accordingly, the two holding members include the first hook portion engaged with the first groove, the second hook portion engaged with the second groove, and the protrusion that biases the scale frame and the detection device in mutually different directions by inserting the protrusion into the gap between the scale frame and the detection device, and the two holding members slide from the first and second sides along the length direction of the scale frame toward the detection device, making it possible to mount the two holding members on the measurement device. Consequently, the two holding members can be mounted without performing work from below the measurement device, and therefore, the ease of a fastening operation can be improved.Further, the two holding members engage the first hook portion at the first groove and the second hook portion at the second groove, and also slide the respective protrusion along the length direction of the scale frame toward the detection device and insert the respective protrusion into the gap, whereby the detection device can be held from two sides. At this time, the protrusion is in sliding contact with the scale frame and the detection device, and the detection device and the scale frame are pre-clamped in mutually different directions, whereby the contact between the scale frame and the detection device can be prevented. Consequently, the pair of holding members can prevent the scale or a sensor of the detection device from being damaged by contact that may occur due to shake or the like during transportation between the scale frame and the detection device.The two holding members are configured by the first hook portion, the second hook portion, and the protrusion, each of which has a simple shape. Therefore, the structure of the two holding members can be simplified. The displacement of the two holding elements is regulated by friction between the first groove and the first hook section, friction between the second groove and the second hook section, and friction between the scale frame and the detection device and the protrusion. Therefore, in positioning the detection device, the detection device can be slid along the length direction of the scale frame by applying a force larger than the friction. Therefore, by using the two holding members, an operator can easily position the detection device.The protrusion is preferably formed such that a thickness of the protrusion inserted into the gap between the scale frame and the detection device becomes gradually thicker as the distance from the detection device increases.According to such a configuration, the protrusion of the two holding members is formed to become gradually thicker as the distance from the detection device increases. Therefore, by simply shifting the two holding members from the first and second sides along the length direction of the scale frame toward the detection device, the scale frame and the detection device can be easily biased in mutually different directions.Preferably, the detection device is attached to the second measurement portion by a fastening tool, and may be attached to the second measurement portion by a fastening tool, respectively, and includes a fastening hole with which the fastening tool is or can be engaged. The two holding members preferably include an insertion hole formed on the main body and through which the fastening tool is inserted, and the two holding members are preferably fastened to the detection device by a locking tool inserted through the insertion hole and into the fastening hole.According to such a configuration, by inserting the locking tool through the insertion hole and into the attachment hole, the detection device and the two holding members can be attached to each other. Consequently, the locking tool can prevent the two holding members from coming off the measurement device and can maintain a holding state of the detection device advantageously. In addition, the locking tool fixes the two holding members using the fixing hole formed on the detection device. Consequently, there is no need to form a screw hole or the like only for fixing the two holding members to the measurement device, and therefore, costs can be lowered.Preferably, the fastening tool includes a fastening shaft engaged with the second measurement portion and a fastening head whose diameter is larger than that of the fastening shaft. The second measurement portion preferably includes a fixing hole that engages with the fixing shaft. The locking tool preferably includes a locking shaft that locks with the insertion hole and the attachment hole, and a locking head whose diameter is larger than that of the insertion hole. Preferably, the insertion hole is formed to have a larger diameter than that of the fixing head, the fixing head is inserted through the insertion hole, and the insertion hole is formed to have a smaller diameter than the locking head.According to such a configuration, the insertion hole is formed to have a diameter larger than that of the attachment head of the attachment tool and also to have a diameter smaller than that of the locking head of the locking tool, and the locking tool includes the locking head whose diameter is larger than that of the insertion hole. Therefore, by removing the locking tool after setting a mounting position of the detection device, the operator can mount the detection device to the second measurement portion using the mounting tool while the two holding members remain mounted. In other words, by replacing the locking tool with the fastening tool only in the transition from the operation of positioning the detection device to the operation of fastening the detection device, various operations can be performed while the two holding members remain mounted, and workability can be improved.The attachment hole preferably includes a recess which is recessed into the detection device to at least partially receive the attachment head by engaging the attachment hole and the attachment shaft.According to such a configuration, by forming the recess on the attachment hole, the attachment head can be buried and accommodated in a surface in which the two holding members are attached without the attachment head protruding. Therefore, after the detection device is attached to the second measurement portion while the two holding members remain mounted, simply by displacing the holding members in the opposite direction from the direction in which the holding members have been displaced in mounting to the measurement device, the holding members can be easily removed from the measurement device.At least one of the two holding members preferably includes a regulating means at an end portion on an opposite side from the detecting device, and the regulating means preferably regulates the displacement of the two holding members by abutting against the side surface of the detecting device.According to another aspect, there is provided a holding method for holding a measurement device including a long scale frame to be fixed to a first measurement portion and accommodating a scale, and a detection device (a detector) to be fixed to a second measurement portion and arranged to be slidable in a length direction of the scale frame, the detection device being configured to detect an amount of relative displacement against over a scale, the holding method comprising: fixing a pair of holding devices (holders) that hold the detection device by being attached to the first and second sides of the scale frame in the length direction by: fixing a main portion of each holding device along a side surface of the scale frame and the detector, engaging a first hook, which protrudes from the main portion with a first groove formed in the scale frame along the length direction of the scale frame, engaging a second hook protruding from the main portion with a second groove formed in the detection device so as to be substantially parallel to the first groove, and positioning a protrusion protruding from the main portion at a gap between the scale frame and the detection device, biasing the scale frame and the detection device in mutually different directions by inserting each protrusion into the gap between the scale frame and the detection device; and in that the two holding devices are slidable from the first and second sides along the length direction of the scale frame toward the detection device.Specifically, the detection device is attached to the second measurement portion by a fastening tool and includes a fastening hole with which the fastening tool can engage, and each holding member of the two holding members includes an insertion hole formed on the main portion and through which the fastening tool is inserted, and each holding member is fastened to the detection device by a locking member inserted through the insertion hole and into the fastening hole.Furthermore, the holding method comprises in particular regulating the displacement of the two holding elements by at least one regulating device which, for at least one holding element, is arranged at one end on a side opposite from the detection device and abuts the side surface of the detection device.According to the above, the control means abuts on the detection device and regulates the displacement of the two holding members, and therefore can prevent excessive displacement of the two holding members. In addition, the control device enables the exact displacement of the two holding elements into the predetermined holding position and also enables the appropriate holding of the detection device.BRIEF DESCRIPTION OF THE DRAWINGSThis invention will be further described in the following detailed description with reference to the multiple drawings set forth herein, by way of non-limiting examples of exemplary embodiments of this invention, in which like reference numerals designate similar parts throughout the several views of the drawings. It should be noted that although embodiments may be described separately, individual features thereof may be combined into further embodiments. FIG. 1A is a front view and FIG. 1B is a cross-sectional view of a measurement device using a pair of support members in a support mechanism according to an embodiment of this invention; FIG. 2 is a perspective view of the measurement device using the pair of holding members; FIG. 3A is a front view and FIG. 3B is a rear view showing a first holding member of the pair of holding members; FIG. 4A is a right side view and FIG. 4B is a left side view of the first holding member; FIG. 5A is a plan view and FIG. 5B is a bottom view of the first holding member; FIG. 6 is a perspective view of the first holding member; FIG. 7A is a front view and FIG. 7B is a rear view showing a second holding member of the pair of holding members; FIG. 8A is a right side view and FIG. 8B is a left side view of the second holding member; FIG. 9A is a plan view and FIG. 9B is a bottom view of the second holding member; FIG. 10 is a perspective view showing a mechanism and a process for fixing the pair of holding members; FIG. 11 is a cross-sectional view showing the mechanism and operation for fixing the pair of holding members of FIG. 10 ; FIG. 12 is a perspective view showing the mechanism and the operation for fixing the pair of holding members of FIG. 11 ; FIG. 13 is a perspective view showing the mechanism and operation for fixing the pair of holding members of FIG. 12 ; FIG. 14 is a cross-sectional view showing the mechanism and operation for fixing the pair of holding members of FIG. 13; FIG. 15 is a cross-sectional view showing the mechanism and operation for fixing the pair of holding members of FIG. 14; FIG. 16 is a cross-sectional view showing a mechanism and a process for fixing a detection device to a second measurement portion using the pair of holding members; FIG. 17 is a cross-sectional view showing the mechanism and operation for fixing the detection device to the second measurement portion of FIG. 16 ; and FIG. 18 is a cross-sectional view showing the mechanism and operation for fixing the detection device to the second measurement portion of FIG. 17.DETAILED DESCRIPTION OF THE INVENTIONThe specifics shown herein are exemplary and are provided for illustrative purposes only of the embodiments of this invention and are presented solely for the purpose of demonstrating what is considered to be the most useful and best understood description of the principles and conceptual aspects of this invention. In this regard, no attempt is made to show structural details of this invention in greater detail than is necessary for a basic understanding of this invention, since the description, taken together with the drawings, will readily suggest to those skilled in the art how the forms of this invention may be practiced.Hereinafter, an embodiment of this invention will be described with reference to the drawings. FIGS. 1A to 2 show a measuring device (a linear scale) using one or more, in particular a pair of holding elements (such as, in particular, holders) in a holding mechanism according to an embodiment of this invention. In particular, FIG. 1A is a front view of a measuring device 1 using one or more, in particular a pair of holding elements (such as in particular holders) 20, and FIG. 1B is a cross-sectional view along a cross-sectional plane A-A in FIG. 1A. FIG. 2 is a perspective view of the measurement device 1 using the pair of holding members 20. As shown in FIGS. 1A to 2, the measurement device 1 that measures a displacement distance between measurement portions includes a measurement device main body 2 and a detection device (such as a detector in particular) 3, and the detection device 3 is attached or attachable to the measurement device main body 2 so as to be displaceable. The measuring device 1 measures the displacement distance at least between a pair of measurement portions (measurable portions) W 1 and W 2. The measurement device main body 2 is to be attached to a first measurement portion W 1, and the detection device 3 is to be attached to a second measurement portion W 2 (see FIG. 1B ).The measurement device main body is configured to include an elongated scale frame 4 and a scale 5 at least partially accommodated or disposed in the scale frame 4. The scale frame 4 is formed to be hollow. The scale 5 comprises in particular a scale carrier, which consists for example of a transparent material such as glass, and one or more scale markings, which are formed on a surface of the scale carrier and in particular consist of or comprise a diffraction grating, for example with a fixed spacing. The scale 5 is to be fixed to an interior of the scale frame 4. In the following description and in each of the accompanying drawings, a length direction of the scale frame 4 and a displacement direction of the detection device 3 are referred to as an X direction, a width direction (inward direction) of the scale frame 4 which is orthogonal to the X direction is referred to as a Y direction, and a vertical direction which is orthogonal to the X and Y directions is referred to as a Z direction.As shown in FIGS. 1A and 1B, the detection device 3 includes a detection device main body 6 to be disposed on an outer side of the scale frame 4 and / or to be attached to the second measurement portion W 2, and a detector 7 to be disposed extending from the detection device main body 6 to the inside of the scale frame 4. The detector 7 is in particular configured to include an optical transmitter 7A arranged along a first surface of the scale 5 and emitting light, and an optical receiver 7B arranged along a second surface of the scale 5 and receiving emitted light that has passed from the optical transmitter 7A out of the scale 5 and acted upon therewith. The detection device 3 generates an electric signal from the emitted light received by the optical receiver 7B, and when the detection device main body 6 receives the electric signal, the detection device 3 detects or determines an amount of relative displacement from the scale 5.Specifically, the scale frame 4 is formed to have a hollow substantially rectangular shape as a whole and includes a fixed part 4A, a first side surface part 4B, a second side surface part 4C, a first bottom surface part 4D, a second bottom surface part 4E, a surface part 4F, and / or a first groove 14. The fixed part 4A is formed by an extruded aluminum alloy member, is located at an upper part of the scale 4, and / or is to be fixed to the first measurement portion W 1. The first side surface part 4B is located on a front surface side of the scale 4, and extends substantially downward (negative Z direction) from the fixed part 4A. The second side surface part 4C extends substantially downward (negative Z direction) from the fixed part 4A so as to face the first measurement portion W 1, and / or is located on a side of the scale 4 opposite to the first side surface part 4B. The first bottom surface part 4D bends substantially from a lower end of the first side surface part 4B and / or extends substantially toward a rear surface side of the scale 4 (in a positive Y direction). The second bottom surface part 4E bends substantially from a lower end of the second side surface part 4C and / or extends substantially toward a front surface side (in a negative Y direction). The surface part 4E is located between the fixing part 4A and the first side surface part 4B. The first groove 14 is formed on the surface part 4F substantially along the length direction (X direction) of the scale frame 4.An open groove 4G which is open substantially along the length direction (X direction) is formed between the first bottom surface part 4D and the second bottom surface part 4E, and the detection device main body 6 and the detector 7 of the detection device 3 are to be connected by the open groove 4G. Also, specifically, a gap 16 is formed between the first bottom surface part 4D and the detection device main body 6. The detection device main body 6 is formed to have a hollow substantially rectangular shape as a whole and / or includes a surface part 6A that adjoins the first bottom surface part 4D and the second bottom surface part 4E of the scale frame 4; a bottom surface part 6B that is located on a bottom surface, a front surface part 6C that is located on a front surface, and / or a back surface part 6D that is located on a back surface. The bottom surface part 6B specifically includes a second groove 15 formed to be substantially parallel to the first groove 14 of the scale frame 4.The detection device main body 6 includes a fastening hole 8 through which a fastening tool 200 is to be at least partially inserted (see FIG. 16 described below) that attaches and fixes the detection device 3 to the second measurement portion W 2. Specifically, the attachment hole 8 is formed ranging from the front surface part 6C to the rear surface part 6D of the detection device main body 6, and by inserting the attachment tool 200 from the front surface part 6C to the rear surface part 6D, the detection device 3 is attached and fixed to the second measurement portion W 2.The above measuring device 1 uses a pair of holding members 20 for holding the detection device 3 on the scale frame 4. as shown in FIGS. 1A to 2, the two holding members 20 are configured by or include a first holding member 21 to be mounted on the measuring device 1 by displacing the first holding member 21 from a first side (negative X-direction side) toward the detection device 3 and a second holding member 22 to be mounted on the measuring device 1 by displacing the second holding member 22 from a second side (positive X-direction side) toward the detection device 3. The two holding elements 20 are in particular formed from or comprise a flexible material, such as a technical plastic for example.The two holding members 20 hold the detection device 3 to the scale frame 4 and restrict the displacement of the detection device 3 to prevent the detection device 3 from moving in an arbitrary direction with respect to the measurement device main body 2 and coming into contact with the scale frame 4 or the like and being damaged during a transport operation until a time of attachment with the measurement portions W 1 and W 2 or the like. Moreover, when the measurement device 1 is fixed to the measurement portions W 1 and W 2, the two holding members 20 are used to position the detection device 3 relative to the measurement device main body 2. In particular, a locking tool 100 is also used to fasten the two holding elements 20 to the measuring device 1.A structure of the two holding members 20 will be described in detail below. Figs. 3A to 6 show the first holding member 21 of the pair of holding members 20, in particular, Figs. 3A to 5B are six planar views of the first holding member 21, Fig. 3A is a front view from the negative Y direction, and Fig. 3B is a rear view from the positive Y direction. FIG. 4A is a left side view from the positive X direction, and FIG. 4B is a right side view from the negative Y direction. FIG. 5A is a plan view from the positive Z direction, and FIG. 5B is a bottom view from the negative Z direction. FIG. 6 is a perspective view of the first holding member 21, and in particular, FIG. 6 is a perspective view showing a rear side of the first holding member 21 facing the measurement device 1.Figs. 7A to 9B show the second holding member 22 of the pair of holding members 20, in particular, Figs. 7A to 9B are six planar views of the second holding member 22, Fig. 7A is a front view from the negative Y direction, and Fig. 7B is a rear view from the positive Y direction. FIG. 8A is a left side view from the positive X direction, and FIG. 8B is a right side view from the negative Y direction. FIG. 9A is a plan view from the positive Z direction, and FIG. 9B is a bottom view from the negative Z direction. In this example, the first holding member 21 of FIGS. 3A to 6 and the second holding member 22 of FIGS. 7A to 9B are specifically formed to be substantially identical or similar to each other and are formed in similar configurations except that a shape of a protrusion 60 and / or a position of a regulator 70 (described later) are right / left symmetrical. Therefore, the first holding member 21 will be described below by way of example with reference to FIGS. 2 to 6.Specifically, as illustrated in FIGS. 2 to 6, the first holding member 21 is configured to include a substantially plate-shaped (planar) main body 30 (such as a main portion) to be attached along a first side (negative Y-direction side) of the width direction of the scale frame 4, a first hook portion 40 to engage with the first groove 14, a second hook portion 50 to engage with the second groove 15, the protrusion 60 protruding toward the gap 16, the regulator 70 that regulates the displacement of the first holding member 21; and / or an insertion hole 80 formed on the main body 30. The main body 30 includes, in particular, a first support portion 31 extending from the protrusion 60 to the first hook portion 40 and / or a second support portion 32 extending from the protrusion 60 to the second hook portion 50. A protrusion 33 for abutting on the first side surface portion 4B of the scale frame 4 is formed on the first support portion 31. In this example, by forming the protrusion 33 on the first support portion 31, in particular, the protrusion 33 facilitates bending of the first support portion 31. the protrusion 33 may be formed at any location on the main body 30 and may have any desired shape, or the protrusion 33 may be omitted insignificantly.The first hook portion 40 is configured by a first extended portion 41 formed extending from the first support portion 31 to the first groove 14 at the surface portion 4F of the scale frame 4 and / or a (substantially acute angle) first tip portion 42 protruding from the first extended portion 41 to the first groove 14. The second hook portion 50 is configured by a second extended portion 51 formed extending from the second support portion 32 to the second groove 15 at the bottom surface portion 6B of the detection device main body 6, and / or a bent second tip portion 52 extending from the second extended portion 51 to the second groove 15.Specifically, the protrusion 60 includes a first abutting surface 61 abutting against the first bottom surface portion 4D of the scale frame 4 and / or a second abutting surface 62 abutting against the surface portion 6A of the detection device main body 6. Specifically, as shown in FIG. 3B, the first abutting surface 61 has an inclination in a direction inclined away from the first bottom surface portion 4D of the scale frame 4, while the inclination is from a first side (negative X-direction side) on which the regulator 70 is formed to a second side (positive X-direction side). In other words, the protrusion 60 is formed such that a thickness between the first abutting surface 61 and the second abutting surface 62 becomes gradually thicker as the distance from the detection device 3 increases.The regulator 70 is formed on the second support portion 32 at an end portion on an opposite side from the detection device 3, and / or regulates the displacement of the first holding member 21 at a certain (predetermined or predeterminable) holding position by abutting against a side surface of the detection device 3. In other words, the regulator 70 may control or regulate an amount of displacement of the protrusion 60 (which is inserted into the gap 16) according to a position at which the regulator 70 is disposed, and / or (particularly, further) positions the insertion hole 80 of the first holding member 21 relative to the attachment hole 8, The control device 70 may be arranged at any desired position on the second support section 32.Specifically, the insertion hole 80 is formed at the second support portion 32 and / or is formed to have a larger diameter than the attachment hole 8 of the detection device 3. In addition, the insertion hole 80 is formed to have a larger diameter than a fixing head 201 of the fixing tool 200 (see FIG. 16 described below) that can fix the detection device 3 to the second measurement portion W 2 (see FIGS. 1A and 1B ); the fixing head 201 is at least partially inserted into the insertion hole 80; and the insertion hole 80 is formed to have a smaller diameter than a locking head 101 of the locking tool 100 (see FIG. 13 ). The lock head 101 is configured to abut on the second support portion 32.Next, a specific mechanism and method for fixing the pair of holding members 20 (the first holding member 21) to the measurement device 1 will be described with reference to FIGS. 10 to 15. FIGS. 11, 14 and 15 are cross-sectional views taken along a sectional plane A-A of FIG. 1A. As shown in FIG. 10, in the process of fixing the first holding member 21, first, the detection device 3 is shifted to a certain (predetermined or predeterminable) position along the length direction (X direction) of the scale frame 4. Then, the first holding member 21 locks the first hook portion 40 to the first groove 14 at a position in the negative X direction and away from the detection device 3, and at which the second hook portion 50 does not contact the detection device 3.At this time, as shown in FIG. 11, when the first holding member 21 is slid in the positive X direction toward the detection device 3, the first hook portion 40 locks to the first groove 14 so that the protrusion 60 is at least partially inserted into the gap 16. The first holding member 21 can also be mounted to the measurement device 1 in another manner, for example, by pressing the first holding member 21 from the negative Y direction to the positive Y direction on the front surface in the width direction (negative Y direction side) of the detection device 3 and the scale frame 4 so that the protrusion 60 is at least partially inserted into the gap 16. In this case, the first holding member 21 has elasticity, and therefore the first hook portion 40 and the second hook portion 50 bend and engage with the first groove 14 and the second groove 15, respectively.Then, as shown in FIG. 12, in a state in which the first hook portion 40 remains engaged with the first groove 14 and the protrusion 60 is at least partially inserted into the gap 16, the first holding member 21 is slid in a direction toward the detection device 3 (positive X direction). By sliding the first holding member 21 in the direction toward the detection device 3, the protrusion 60 slides against the first bottom surface portion 4D of the scale frame 4 and the surface portion 6A of the detection device main body 6, and the detection device 3 and the scale frame 4 are biased in mutually different directions. The first holding member 21 is slid until the regulator 70 abuts the first side surface (negative X-direction side) of the detection device 3.Then, as shown in FIG. 13, after the regulator 70 of the first holding member 21 abuts on the first side surface (negative X-direction side) of the detection device 3, the locking tool 100 is engaged with the attachment hole 8 via the insertion hole 80. Specifically, as illustrated in FIG. 14, in this example, the attachment hole 8 is configured by or includes a recess 8A, a first hole portion 8B, and a second hole portion 8C. Specifically, the fixing hole 8 is formed continuously to the rear surface portion 6D of the detection device main body 6, and a thread is cut in the first hole portion 8B so as to be able to screw a second lock shaft 102B (described below) while no thread is cut in the second hole portion 8C.In addition, the locking tool is constituted by or includes the locking head 101 having a larger diameter than the insertion hole 8 80; and / or the locking shaft 102 protruding from the locking head 101 and engaging with the attachment hole 8 via the insertion hole 80. The locking shaft 102 is formed by or comprises a first locking shaft 102A which is at least partially inserted into the depression 8A via the insertion hole 80 and / or a second locking shaft 102B on which a thread is cut. Consequently, as shown in FIG. 15, by operating (e.g., by rotating) the locking tool 100, the first hole portion 8B and the second locking shaft 102B are connected (e.g., screwed together), and since the first holding member 21 and the detection device 3 are secured to the measurement device 1. When the first locking shaft 102A and the second locking shaft 102B are at least partially inserted through the insertion hole 80 to fix the first holding member 21, a state is established in which the first holding member 21 and the detection device 3 are fixed without the locking tool 100 passing through the detection device 3. By performing a similar operation also on the second holding member 22, the second holding member 22 and the detection device 3 can be secured to the measurement device 1 using the locking tool 100.Next, a mechanism and an operation for attaching the detection device 3 to the second measurement portion W 2 will be described with reference to FIGS. 16 to 18. FIGS. 16 to 18 are cross-sectional views taken along the sectional plane A-A of FIG. 1A. As shown in FIG. 16, a fixing hole 8D is formed at the second measurement portion W 2, the fixing hole 8D communicating with the second hole portion 8C of the attachment hole 8 to enable the attachment of the detection device 3. In this example, the fastening tool 200 is configured by the fastening head 201 and the fastening shaft 202, which is formed with a thread from the fastening head 201 to an end portion, and which is screwed to the fixing hole 8D. In addition, the fixing hole 8 includes the recess 8A which is recessed to at least partially receive the fixing head 201, particularly by screwing the fixing hole 8D and the fixing shaft 202 together. The fixing head 201 is formed with a larger diameter than that of the fixing shaft 202 and is formed into a size that can be accommodated in the recess 8A.An example of the process of attaching the detection device 3 to the second measurement section W 2 is to first position the detection device 3 at a certain (predetermined or predeterminable) position along the length direction (X direction) of the scale frame 4 by sliding the detection device 3 while the pair of holding members 20 and the locking tool 100 are mounted thereon (see FIG. 2 ). Since the two holding elements 20 are mounted, in this example the displacement of the detection device 3 is regulated in particular by friction between the first groove 14 and the first hook section 40, friction between the second groove 15 and the second hook section 50 and / or friction between the scale frame 4 and the detection device and the projection 60. In positioning the detection device 3, the detection device 3 can be slid along the length direction of the scale frame 4 by applying a force exceeding the friction. Consequently, by applying a force exceeding the friction from the two holding members 20 in a state where the locking tool 100 is mounted, the detection device 3 is slid and positioned at the determined (predetermined or predeterminable) position along the length direction (X direction) of the scale frame 4. Then, as shown in FIG. 16, the locking tool 100 is pulled out of the first holding member 21. Then, the fastening tool 200 is at least partially inserted through the insertion hole 80 and the fastening hole 8 through which the locking tool 100 before being pulled out has been inserted.Then, as shown in FIG. 17, the fastening tool 200 fixes the detection device to the second measurement portion W 2. The first hole portion 8B is formed with a diameter larger than that of the fixing shaft 202, and therefore, when the fixing tool 200 is inserted into the fixing hole 8, the fixing hole 8D passes through the fixing hole 8D without being screwed onto the first hole portion 8B and the second hole portion 8C. The fixing shaft 202 passes through the detection device 3 and fixes the second measurement portion W 2 and the detection device 3 by screwing together with the fixing hole 8D. Then, by screwing the fixing shaft 202 and the fixing hole 8D together, the fixing head 201 is received in the recess 8A of the fixing hole 8A. Therefore, as shown in FIG. 18, after the detection device 3 is attached to the second measurement portion W 2 by sliding the first holding member 21 in the negative X direction with the attachment tool 200, the first holding member 21 can be detached from the measurement device 1 in a simple action. The detection device 3 can be fixed to the second measurement portion W 2 using the fixing tool 200 by performing a similar operation also on the second holding member 22.In this way, the following effects and advantages can be obtained according to this embodiment: (1) The two holding members 20 include, in particular, the first hook portion 40 engaged with the first groove 14, the second hook portion 50 engaged with the second groove 15, and / or the protrusion 60 biasing the scale frame 4 and the detection device 3 in mutually different directions, in particular, by inserting the protrusion 60 into the gap 16, and the two holding members 20 slide from the first and second sides of the length direction of the scale frame 4 (X direction) toward the detection device 3, thereby enabling mounting of the two holding members 20 on the measurement device 1. Consequently, the two holding members 20 can be assembled without performing work from below the measurement device 1, and therefore, the convenience of a fastening operation can be improved. (2) Specifically, the two holding members 20 engage the first hook portion 40 at the first groove 14 and engage and / or slide (also) the respective projections 60 along the length direction of the scale frame 4 (X direction) toward the detection device 3 and guide the respective projections 60 into the gap 16, enabling holding of the detection device 3 from two sides, at the second groove 15. At this time, the protrusion 60 makes sliding contact with the scale frame 4 and the detection device 3, and the scale frame 4 and the detection device 3 are biased in mutually different directions, making it possible to prevent the contact between the scale frame 4 and the detection device 3. Consequently, the two holding members 20 can prevent the scale 5 or sensors (the detector 7) of the detection device 3 from being damaged by contact that may occur between the scale frame 4 and the detection device 3 by shaking or the like during transportation. (3) The two holding members 20 are configured by or include the first hook portion 40, the second hook portion 50, and the protrusion 60, each of which has a simple shape. Therefore, the structure of the two holding members 20 can be simplified. (4) The displacement of the two holding members 20 is controlled in particular by friction between the first groove 14 and the first hook portion 40, friction between the second groove 15 and the second hook portion 50, and / or friction between the scale frame 4 and the detection device 3 and the protrusion 60. Therefore, in positioning the detection device 3, the detection device 3 can be slid along the length direction of the scale frame 4 (X direction) by applying a force exceeding the friction. Consequently, by using the two holding members 20, an operator can easily position the detection device 3. (5) The protrusion 60 is formed to become gradually thicker as the distance from the detection device 3 increases. Therefore, the scale frame 4 and the detection device 3 can be easily biased in different directions from each other only by sliding the two holding members 20 from the first and second sides along the length direction of the scale frame 4 (X direction) toward the detection device 3. (6) By at least partially inserting the locking tool 100 through the insertion hole 80 and into the attachment hole 8, the detection device 3 and the two holding members 20 can be attached to each other. Consequently, the locking tool 100 can prevent the two holding members 20 from coming off the measurement device 1 and can maintain a holding state of the detection device 3 advantageously. (7) The locking tool 100, in particular, fixes the two holding members 20 by using the fixing hole 8 formed on the detection device 3. Consequently, there is no need to form a screw hole or the like only to fix the two holding members 20 to the measurement device 1, and thus costs can be lowered. (8) Specifically, the insertion hole 80 is formed to have a diameter larger than that of the attachment head 201 of the attachment tool 200, and / or (also) to have a diameter smaller than that of the locking head 101 of the locking tool 100, and the locking tool 100 includes the locking head 101 whose diameter is larger than that of the insertion hole 80. Therefore, by removing the locking tool 100 after setting a mounting position of the detection device 3, the operator can mount the detection device 3 to the second measurement portion W 2 using the mounting tool 200 while the two holding members 20 remain mounted. In other words, simply by replacing the locking tool 100 with the fastening tool 200 in the transition from the operation of positioning the detection device 3 to the operation of fastening the detection device 3, various operations can be performed while the two holding members 20 remain mounted, and workability can be improved. (9) By forming the recess 8A on the mounting hole 8, the mounting head 201 can be recessed and accommodated in a surface to which the two holding members 20 are mounted without the mounting head 201 protruding. Therefore, after the detection device 3 is attached to the second measurement portion W 2 while the two holding members 20 remain mounted, the holding members 20 can be easily removed from the measurement device 1 by simply displacing the holding members 20 in the direction opposite to the direction in which the holding members 20 have been displaced in mounting to the measurement device 1. (10) The control device 70 abuts on the detection device 3 in particular, and controls the displacement of the two holding members 20, and can therefore prevent the excessive displacement of the two holding members 20. In addition, the control device 70 enables the exact displacement of the two holding elements 20 to the determined (predetermined or predeterminable) holding position and also enables the appropriate holding of the detection device 3.ModificationsMoreover, this invention is not limited to the above-described embodiment, and includes modifications and improvements within a scope that can achieve the advantages of this invention. For example, in the above-described embodiment, a case where a holding mechanism is used on an optical measurement device 1 (linear scale) is described. However, any device including a detection unit slidably disposed on a measurement device main body is suitable as a measurement device, and a shape or format, a detection method, and the like of the detection device are not particularly limited.In the above-described embodiment, the scale frame 4 of the measurement device main body 2 is formed substantially in a hollow substantially rectangular shape as a whole. However, the shape of the scale frame 4 is not limited to a rectangle, and may be any other shape. In the above embodiment, the first groove 14 is formed in the surface portion 4F of the scale frame 4, and / or the second groove 15 is formed in the bottom surface portion 6B of the detection device main body 6. However, the first groove 14 may instead be formed in the fixed portion 4A or the first side surface portion 4B of the scale frame 4, and the second groove 5 may instead be formed in the front surface portion 6C of the detection device main body 6. In other words, as long as the first hook portion 40 can engage with the first groove 14 and the second hook portion 50 can engage with the second groove 15 to hold the scale frame 4 and the detection device 3, the first groove 14 and the second groove 15 can be formed on any surface.In the above-described embodiment, the first tip portion 42 of the first hook portion is formed in an acute angle shape, and / or the second tip portion 52 of the second hook portion 50 is formed in a curved shape, in particular. However, as long as the tip portions have a shape engageable with the first groove 14 and the second groove 15, respectively, the tip portions may have any shape. The first hook section 40 is also configured to point in particular downward (negative Z direction) and the second hook section 50 is configured to point in particular upward (positive Z direction). However, as long as the hook portions can engage with the first groove 14 and the second groove 15, respectively, the hook portions may be formed facing in any desired direction.In the above embodiment, the two holding members 20 are mounted on the side substantially opposite to the fixed portion 4A fixed to the first measurement portion W 1. However, the two holding members 20 may instead be mounted on a surface on the side of the fixed portion 4A. Also, the two holding members 20 are flexible, but the two holding members 20 may have no flexibility instead. In the above-described embodiment, the first holding member 21 and the second holding member 22 are formed substantially with right / left symmetry. However, the first holding member 21 and the second holding member 22 may be formed without right / left symmetry and may be formed to be different from each other. In other words, as long as the detection device 3 can be held on the scale frame 4 by the first holding member 21 and the second holding member 22, the first holding member 21 and the second holding member 22 may be formed in any shape.In the above embodiment, the slope is formed on the first stopper surface 61 of the protrusion 60, in particular. Instead, an inclination may be formed on the second stop surface 62 of the protrusion 60, or an inclination may be formed on the first stop surface 61 and on the second stop surface 62. Also, the first stopper surface 61 and the second stopper surface 62 may be formed without being inclined by forming the first stopper surface 61 and the second stopper surface 62 to be parallel and thicker than the gap 16. In addition, the first stop surface 61 and the second stop surface 62 may be formed with surface unevenness instead of planar surfaces, or may be formed with waviness. In other words, the protrusion 60 should be formed such that the thickness of the protrusion 60 inserted into the gap 16 between the scale frame 4 and the detection device main body 6 increases, and as long as the scale frame 4 and the detection device 3 can be fixed, the protrusion 60-+may have any shape. Also, the two holding members 20 are formed with the insertion hole 80 on the main body 30, but the insertion hole 80 may not be formed. Furthermore, the control device 70 can have any desired shape or can be omitted.In the above-described embodiment, the insertion hole 80 of the two holding members 20 is formed to have a diameter larger than that of the attachment hole 8 of the detection device 3. However, the insertion hole 80 may be formed to have the same diameter as the attachment hole 8. In other words, the detection device 3 and the second measurement portion W 2 should be able to be fastened to each other by the fastening tool 200 in a state where the two holding members 20 are mounted on the measurement device 1, and therefore the insertion hole 80 should be formed with a diameter that enables the insertion of the fastening tool 200. Also, the recess 8A of the fastening hole 8 is formed to be able to receive the fastening head 201, the first hole portion 8B is formed with the thread screwed to the second locking shaft 102B of the locking tool 100, and the second hole portion 8C is formed without the thread. However, a thread may be cut in each of the recess 8A, the first hole portion 8B and the second hole portion 8C, or neither may be cut in a thread. The depression 8A can also be omitted. In other words, as long as the two holding members 20 and the measurement device 1 can be fixed to each other using the locking tool 100, and the detection device 3 can be fixed to the second measurement portion W 2 using the fixing tool 200, an interior of the fixing hole 8 can be formed arbitrarily.The above-described embodiment uses the locking tool 100 having a thread. However, the locking tool 100 may perform the fastening by, for example, being pressed into resin or the like. In other words, the locking tool 100 should be suitable for insertion through the insertion hole 80 and into the attachment hole 8 and for attaching the detection device 3 to the two holding members 20, and any means may be used to achieve this. Also, the insertion hole 80 of the two support members 20 is formed to have a diameter larger than that of the recess 8A of the attachment hole 8, and is formed in a circular shape. As long as the insertion hole 80 is formed so that its diameter is larger than that of the attachment head 201 of the attachment tool 200 and its diameter is smaller than that of the locking head 101 of the locking tool 100, the insertion hole 80 may be formed in any shape.As mentioned above, in a measuring apparatus including a scale frame housing, a scale and a detecting device which detects an amount of relative displacement to the scale, this invention can be advantageously used in a holding mechanism which holds the detecting device of the measuring apparatus on the frame housing.Thus, a holding mechanism for use in a measuring device includes a first groove, a second groove and one or more, in particular a pair of holding elements, which hold the detection device by being fastened to a first and a second side, or a first and a second side part in the length direction of a scale frame. The pair of support members includes a plate-shaped main body, a first hook portion engaged with the first groove, a second hook portion engaged with the second groove, and / or a protrusion protruding from the main body and positioned at a gap. The two holding members are slid toward the detection device from first and second sides along the length direction of the scale frame, and the protrusion is inserted into the gap, and thereby the protrusion biases the scale frame and the detection device in mutually different directions.It should be understood that the foregoing examples have been described for purposes of illustration only and are not to be considered as limiting the present invention in any way. While this invention has been described with reference to exemplary embodiments, it is to be understood that the words used herein are words of description and representation, rather than words of limitation. Changes may be made within the scope of the appended claims as set forth herein and in amended form without departing from the scope and spirit of this invention in its aspects. While this invention has been described herein with reference to particular structures, materials and embodiments, this invention is not intended to be limited to the details disclosed herein, but this invention extends to all functionally equivalent structures, methods and applications as fall within the scope of the appended claims.This invention is not limited to the above-described embodiments, and various variations and modifications may be possible without departing from the scope of this invention.

Claims

A holding mechanism for a measurement device including a long scale frame (4) to be fixed to a first measurement portion (W1) and accommodating a scale (5), and a detector (3; 7) to be fixed to a second measurement portion (W2) and arranged to be capable of displacement in a length direction of the scale frame (4), wherein the detector (3; 7) is configured to detect an amount of relative displacement with respect to the scale (5), the holding mechanism comprising: a first groove (14) formed in the scale frame (4) along the length direction of the scale frame (4); a second groove (15) formed in the detector (3; 7) to be substantially parallel to the first groove (14); and a pair of holders (20) configured to hold the detector (3; 7) by being attached to first and second sides of the scale frame (4) in the length direction, wherein: each holder (21, 22) of the pair of holders (20) comprises: a main portion (30) to be attached along a side surface of the scale frame (4) and the detector (3; 7); a first hook (40) protruding from the main portion (30) and adapted to engage with the first groove (14); a second hook (50) protruding from the main portion (30) and adapted to engage with the second groove (15); and a protrusion (60) protruding from the main portion (30) and adapted to engage with a gap (16) between the scale frame (4) and the detector (3; The method is described in detail in which the pair of holders (20) are displaceable from the first and second sides toward the detector (3; 7) along the length direction of the scale frame (4), and each protrusion (60) is insertable into the gap (16) between the scale frame (4) and the detector (3; 7) such that each protrusion (60) biases the scale frame (4) and the detector (3; 7) in mutually different directions, a thickness of each protrusion (60) being gradually thicker as the distance from the detector (3; 7) increases.The holding mechanism according to the preceding claim, wherein: the detector (3; 7) is attachable to the second measurement portion (W2) by a fastening tool (200), and includes a fastening hole (8) with which the fastening tool (200) can engage.The holding mechanism according to claim 2, wherein: each holder (21, 22) of the pair of holders (20) includes an insertion hole (80) which is formed on the main portion (30) and through which the fastening tool (200) is inserted, and each holder (21, 22) can be fastened to the detector (3; 7) by a locking tool (100) which is inserted through the insertion hole (80) and into the fastening hole (8).The holding mechanism according to claim 3, wherein the fastening tool (200) comprises: a fastening shaft (202) to be engaged with the second measurement portion (W2); and a fastening head (201) having a diameter larger than that of the fastening shaft (202); wherein the second measurement portion (W2) comprises: a fixing hole (8D) to be engaged with the fastening shaft (202), wherein the locking tool (100) comprises: a locking shaft (102) to be locked with the insertion hole (80) and the fastening hole (8); and a locking head (101) having a diameter larger than that of the insertion hole (80), and wherein the insertion hole (80) is formed to have a diameter larger than that of the fixing head (201), the fixing head (201) is inserted through the insertion hole (80), and the insertion hole (80) is formed to have a diameter smaller than that of the locking head (101).The holding mechanism according to claim 4, wherein the fixing hole (8) includes a recess (8A) which is recessed into the detector (3; 7) to receive the fixing head (201) by engaging the fixing hole (8D) with the fixing shaft (202).The holding mechanism according to any one of the preceding claims, wherein at least one of each holder (21, 22) further includes a regulating device (70) at an end on a side opposite from the detector (3; 7), the regulating device (70) being configured to regulate the displacement of the pair of holders (20) by abutting against the side surface of the detector (3; 7).A holding method for holding a measurement device including a long scale frame (4) to be fixed to a first measurement portion (W1) and accommodating a scale (5), and a detector (3; 7) to be fixed to a second measurement portion (W2) and arranged to be capable of displacement in a length direction of the scale frame (4), wherein the detector (3; 7) is configured to detect an amount of relative displacement with respect to the scale (5), the holding method comprising: fixing a pair of holders (20) including the detector (3; 7) by being fixed to first and second sides of the scale frame (4) in the length direction by: fixing a main portion (30) of each bracket (21, 22) along a side surface of the scale frame (4) and the detector (3; 7); engaging a first hook (40) protruding from the main portion (30) with a first groove (14) formed in the scale frame (4) along the length direction of the scale frame (4); engaging a second hook (50) protruding from the main portion (30) with a second groove (15) formed in the detector (3; 7) so as to be substantially parallel to the first groove (14); and positioning a protrusion (60) protruding from the main portion (30) at a gap (16) between the scale frame (4) and the detector (3; 7), biasing the scale frame (4) and the detector (3; 7) in mutually different directions by inserting each protrusion (60) into the gap (16) between the scale frame (4) and the detector (3; 7) and in that the pair of holders (20) is slidable from the first and second sides along the length direction of the scale frame (4) toward the detector (3; 7), a thickness of each protrusion (60) being gradually thicker as the distance from the detector (3; 7) increases.The holding method according to claim 7, wherein: the detector (3; 7) is fixed to the second measurement portion (W2) by a fastening tool (200) and includes a fastening hole (8) with which the fastening tool (200) can engage; each holder (21, 22) of the pair of holders (20) includes an insertion hole (80) which is formed on the main portion (30) and through which the fastening tool (200) is inserted; and each holder (21, 22) is fixed to the detector (3; 7) by a locking tool (100) which is inserted through the insertion hole (80) and into the fastening hole (8).The holding method according to claim 7 or 8, further comprising regulating the displacement of the pair of holders (20) by at least one regulating device (70) which is arranged for at least one holder (21, 22) at an end on a side opposite to the detector (3; 7) and abuts the side surface of the detector (3; 7).

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