JP2014105874A - Fastening device for fastening element to supporting portion with compensation of thermal expansion difference, and optical apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for fastening both of a supporting portion and an element sensitive to thermal expansion difference.SOLUTION: A fastening device for fastening an element 1 to a supporting portion 2, includes at least one stud 4 fixed to the element, and at least one connection ring 5 to be connected to the supporting portion. The connection ring 5 surrounds the stud to load clamp force to the stud, and the connection ring has an internal ring 6 kept into contact with the stud, and an external ring 7 to be connected to the supporting portion. The internal ring and the external ring are coaxial around the stud, and provided with means for compensating at least a part of thermal expansion difference to approximately unify the clamp force over a prescribed temperature range, to cooperate with each other.

Description

  The present invention relates to a device for fastening an element to a support and to an apparatus comprising such a device.

  It is known that an observation satellite is equipped with an optical device whose temperature is not controlled. An optical instrument, such as a telescope, is a mirror attached to a support that allows some of the optical elements to be moved relative to each other, for example to scan a portion of the surface of the earth. Having optical elements including.

  The performance of an optical instrument depends primarily on the manufacturing quality of the optical element, and secondly on the stress applied to the optical element, and once the satellite is in orbit, these stresses are It can cause deformation of the optical elements or even damage them.

  Because glass has better polishing properties than other materials that can be used for mirror manufacture, instrument mirrors are generally made of glass when a generally high level of performance is required. The glass mirror is then bonded and bonded to its support, which is generally made of metal.

  Nonetheless, in an optical instrument onboard a satellite that is not temperature controlled, the temperature is from the temperature on the ground, that is, generally in the range of 10 ° C to 40 ° C, depending on geographical location and timing, in space. The temperature drops to approximately 80K.

  Glass has a small or zero coefficient of thermal expansion, and its metal support has a relatively large coefficient of thermal expansion, causing a high level of stress in the bond and mirror. This stress causes a difference in thermal expansion and damages the adhesive film or deforms the mirror, which is detrimental to the performance of the optical apparatus. Therefore, metal mirrors are preferred over glass mirrors in these applications because metal mirrors provide mechanical fastening possibilities that are better configured for these constraints. However, as mentioned above, the optimum optical quality that can be obtained with a metal mirror is not as favorable as the optimum quality of a glass mirror.

  It is an object of the present invention to provide means for fastening together a support and elements that are sensitive to thermal expansion differences.

  In order to achieve this object, the present invention is a fastening device for fastening an element to a support, comprising at least one stud fixed to the element and at least one connection ring for connection to the support. And the connection ring surrounds the stud to apply a clamping force to the stud, and the connection ring has an inner ring in contact with the stud and an outer ring for connection to the support. The inner ring and the outer ring are coaxial about the stud and have means for compensating for at least a portion of the differential thermal expansion so that the clamping force is substantially constant over a predetermined temperature range. A cooperating fastening device is provided.

  Thus, the inner ring contacts the stud, the outer ring contacts the support, the rings cooperate with each other and cooperate with compensation means for absorbing differential expansion. As a result, the clamping force is constant over a predetermined range of temperatures.

  In a preferred embodiment, the outer ring comprises two parts that are separated from each other by an axial groove and have at least one peripheral clamping member that joins the part by crossing the groove. Preferably, the clamping member is supported against a part of the part by an elastic element.

  Elastic elements are particularly useful when there is uncertainty about the difference in thermal expansion over the entire temperature range, especially when the difference in thermal expansion changes nonlinearly.

  In a preferred embodiment, the inner ring has a radial groove configured to promote radial expansion of the inner ring, and preferably the inner ring extends from an outer peripheral edge of the inner ring. And a second continuous radial groove extending from the inner peripheral edge of the inner ring, wherein the inner ring has a radial groove in each of the first continuous radial grooves. Adjacent groove pairs are separated in pairs symmetrically so as to separate the two pairs of radial grooves of the second continuous radial groove.

  The invention further provides an optical instrument having an optical element fastened to a support by at least one device of the type described above.

  Other features and advantages of the present invention will become apparent with reference to the following detailed description of specific, non-limiting embodiments of the present invention.

  The attached drawings will be described.

It is a fragmentary perspective view of the optical apparatus which concerns on this invention. It is detail drawing of the area | region II of FIG. 1 which shows the fastening apparatus based on this invention in detail. FIG. 4 is a partial view of an inner ring and an outer ring of a connection ring according to the present invention.

  By way of illustration, the optical instrument according to the present invention may be a telescope for mounting on a satellite. Since the optical instrument is not temperature controlled, it must be able to withstand temperatures of about 10 ° C. to 40 ° C. on the ground and about 80K in orbit. This is a substantially continuous drop between these two extreme temperatures.

  Referring to the figure, the optical instrument comprises an optical element, in this example comprising a mirror 1 fastened to a support 2 by means of three fastening devices indicated generally by the reference numeral 3. The mirror 1 is made of glass, and more specifically is made of glass of the type manufactured by Schott, a supplier as Zerodur®. Such glasses have the special feature of having a coefficient of thermal expansion of approximately zero.

  Each fastening device 3 has a cylindrical stud 4 fixed to the mirror 1. The stud 4 protrudes radially outward from the periphery of the mirror 1 and is configured symmetrically at the periphery of the mirror 1. The studs 4 extend at 120 ° relative to each other and are formed integrally with the mirror 1.

  Each fastening device comprises a ring for connection with the support 2, indicated generally by the reference numeral 5 and surrounding the stud 4 in order to generate a clamping force on the stud 4. .

  The connection ring 5 includes an inner ring 6 that contacts the stud 4 and an outer ring 7 for connection to the support portion 2. The inner ring 6 and the outer ring 7 are coaxial around the stud 4.

  The inner ring 6 has a radial groove configured to promote the radial expansion of the inner ring 6. More precisely, the inner ring 6 has a first continuous radial groove 6.1 extending from the outer peripheral edge of the inner ring 6 and a second continuous radial direction extending from the inner peripheral edge of the inner ring 6. And a groove 6.2. The radial grooves 6.1, 6.2 of the inner ring are such that each adjacent pair of grooves in the first continuous radial groove 6.1 is a radial groove of the second continuous radial groove 6.2. The two pairs are separated symmetrically so as to separate the two pairs.

  The outer ring 7 has two parts 7.1, 7.2 separated from each other by an axial groove 8, and by traversing the groove 8 and parts 7.1, 7.2 its part 7.1, 7.2 Having two peripheral clamping members that join together. The clamping members each have a head that bears against the part 7.1 and a threaded end that engages in a nut 10 that bears against the part 7.2 via a resilient element such as a spring 11. , A screw 9 having The spring 11 may be a helical compression spring or may be a laminate of elastically deformable Belleville type washers.

  The outer ring 7 has two flat portions 7.3 symmetrically fastened to the end portions of the respective support arms 2. In this illustration, the arms extend at approximately 120 ° relative to each other and are structures known per se.

  In this illustration, the material of the inner ring 6 has a coefficient of thermal expansion that is greater than the coefficient of thermal expansion of the material of the outer ring 7. The inner ring 6 is made of steel and the outer ring 7 is made of a material having a low coefficient of thermal expansion. Illustratively, the metal in question is a relatively high concentration of nickel-containing iron, such as an alloy sold by the supplier IMPHY ALLOYS as Invar®. It is an alloy.

  When the optical instrument is exposed to a temperature drop, the outer ring 7 and the inner ring 6 tend to contract, but the spring 11 is such that the clamping force applied to the stud 4 is substantially constant over a predetermined temperature range. As is, it absorbs changes in the length of the outer ring 7. This is caused by the compensation for the differential thermal expansion made possible by the radial grooves 6.1, 6.2 and the spring 11 of the inner ring 6.

  The configuration of the radial grooves 6.1, 6.2 makes it possible to avoid the generation of unnecessary torque in the stud 4 and / or the outer ring 7 due to the contraction of the inner ring 6.

  Naturally, the invention is not limited to the described embodiments, but encompasses any variant within the scope of the invention as defined by the claims.

  In particular, the present invention is for any optical element, such as a mirror lens, a sensor, and more generally any element of shape and / or arrangement that must be relatively insensitive to thermal expansion differences. Configured. Thus, the present invention can be used to fasten any type of element to another element outside the field of optics.

  The outer ring may be clamped to the inner ring by a clamping member other than those described. If the change in expansion difference over the entire temperature range is known, the elastic element can be omitted.

  The connecting ring may have a different structure than that described, for example, a cone in which the compensation of the clamping force and differential thermal expansion results from the relative range in which the inner ring is engaged in the outer ring. An inner ring and an outer ring cooperating via a shaping surface may be provided, and the clamping force engaging one in the other is loaded by the elastic member with an adjustable prestress.

  The present invention may be applied to temperature ranges other than those described.

DESCRIPTION OF SYMBOLS 1 Mirror 2 Support part 3 Fastening device 4 Stud 5 Connection ring 6 Inner ring 6.1 1st continuous radial groove 6.2 2nd continuous radial groove 7 Outer ring 7.1 Separated part 2 Separated parts 7.3 Flat part 8 Axial groove 9 Clamp member 10 Clamp member 11 Elastic element

Claims (10)

A fastening device for fastening the element to the support (2),
Comprising at least one stud (4) fixed to the element and at least one connection ring (5) for connection to the support;
The connecting ring (5) surrounds the stud to apply a clamping force to the stud;
The connection ring has an inner ring (6) in contact with the stud, and an outer ring (7) for connecting to the support part,
The inner and outer rings are coaxial about the stud and have means for compensating for at least part of the thermal expansion difference such that the clamping force is substantially constant over a predetermined temperature range; Fastening devices that cooperate with each other.   The outer ring (7) comprises two parts (7.1, 7.2) separated from each other by an axial groove (8), at least connecting the parts by traversing the axial groove Fastening device according to claim 1, comprising one peripheral clamping member (9, 10).   Fastening device according to claim 2, wherein the clamping member (9, 10) is supported against one of the parts via an elastic element (11).   Fastening device according to claim 1, wherein the inner ring (6) has a radial groove (6.1, 6.2) configured to promote radial expansion of the inner ring.   The inner ring (6) has a first continuous radial groove (6.1) extending from the outer peripheral edge of the inner ring and a second continuous radial direction extending from the inner peripheral edge of the inner ring. Fastening device according to claim 1, comprising a groove (6.2).   The radial groove (6.1, 6.2) of the inner ring is a radial groove of the second continuous radial groove, each pair of adjacent grooves in the first continuous radial groove. The fastening device according to claim 5, wherein the two pairs are separated symmetrically in pairs so as to separate the two pairs.   When the element is made of glass, the stud (4) is made of glass, the inner ring (6) is made of steel, and the outer ring (7) is alloyed with nickel to increase the strength. The fastening device according to claim 1, wherein the fastening device is made of steel.   Fastening device according to claim 1, wherein the outer ring (7) has at least one flat part (7.3) for fastening to one end of a support arm.   Optical instrument comprising an optical element (1) fastened to a support (2) by at least one fastening device according to any one of the preceding claims.   The optical apparatus according to claim 9, wherein the glass mirror (1) has a plurality of studs (4) that are symmetrically separated at the periphery of the glass mirror and formed integrally with the glass mirror.

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