Pre-tightening spring washer, assembly including the pre-tightening spring washer and manufacturing process for the pre-tightening spring washer

Abstract

The present invention relates, in general, to a pre-tightening spring washer, comprising a discoidal body formed in one piece, the discoidal body being provided with a central hole, the discoidal body having a first contact face and a second contact face situated opposite each other in a thickness direction of the discoidal body, the discoidal body being a solid of revolution formed by the rotation of a radial section around a central axis of rotation by 360 degrees, the central axis of rotation coinciding with a central axis of the central hole, the radial section having a first linear segment and a second opposing linear segment, the first contact face being defined by the rotation of the first linear segment, the second contact face being defined by the rotation of the second linear segment,an axis of intermediate diameter being defined such that it passes through a midpoint of the second linear segment and extends normally to the second linear segment, the radial section having specular symmetry with respect to the axis of intermediate diameter, the axis of intermediate diameter not being parallel to the central axis of rotation, the first linear segment being curved, the concavity of the curved shape being oriented towards the midpoint of the second linear segment, a point of intersection of the axis of intermediate diameter and the first linear segment being a point such that a vertical distance measured from this point to a straight segment connecting the two ends of the second linear segment is the greatest of the vertical distances measured from all points on the first linear segment to said straight segment, the minimum thickness between the first and second contact faces of the discoid body being,in an unloaded state of the pre-tightened spring washer, greater than 3 / 4 of the unloaded height of the discoid body and greater than 1 / 12 of the unloaded outside diameter of the discoid body.

Description

Title of the invention: Pre-tightening spring washer, assembly comprising the pre-tightening spring washer and method of manufacturing the pre-tightening spring washer Domain

[0001] The present invention relates generally to a pre-tightening spring washer, in particular to a curved pre-tightening spring washer and, more particularly, to an assembly comprising such a pre-tightening spring washer. Background

[0002] In the mechanical field, if two components are to be joined by means of screw fasteners such as a screw and a nut, a washer is usually placed between one of the screw fasteners and one of the components to be joined in order to disperse a force exerted by the screw fastener on the component and to increase the friction between them so as to create an anti-loosening effect. For example, a conventional washer is usually a flat or open washer. However, such a conventional washer is only suitable in the case of static fastening. In the case of static fastening, a load supported by the already fixed component is a static load.However, where the load carried by the already fixed component is a variable dynamic load, the component and the washer cooperating with it shall be designed with consideration of a way of compensating for both a loss of displacement caused by the variable dynamic load and a loss of fixing force (also called pre-tightening force) caused by the variable dynamic load.

[0003] Although there is a disc-shaped washer or a disc-shaped spring in the prior art, the disc-shaped washer or the disc-shaped spring of the prior art cannot compensate for the loss of displacement or the loss of pre-tightening force caused by a relatively large dynamic variable load. For example, although the disc-shaped washer of the prior art is provided with a rolling-formed toothing on its upper and lower flat surfaces, the rolling-formed toothing has an anti-slip effect and an anti-loosening effect only in the case of a static load. An elastic force produced by the rolling-formed toothing is too small to compensate for the loss of displacement or the loss of pre-tightening force.As another example, even though the prior art disc spring can be designed to compensate for the loss of displacement and loss of pre-tightening force caused by static loading to some extent, the prior art disc spring cannot be designed to compensate for the loss of displacement and . loss of pre-tightening force caused by varying dynamic load.

[0004] Modern manufacturing plant equipment, particularly chemical manufacturing equipment, commonly includes pipes for the transport of high pressure and / or high temperature fluids, including corrosive fluids. A flange is usually located between two pipes for their tight coupling by butting. Such pipes are used in operating conditions in which temperature or pressure variations may commonly occur, and are subject to strong mechanical vibrations that may occur frequently. Under these operating conditions, the prior art disc spring does not meet the requirements for high temperature resistance, tightness, and support of varying dynamic loads. It would be desirable to design a new pre-tightening spring washer. Abstract

[0005] The present invention aims to provide a novel pre-tightening spring washer, in particular a curved pre-tightening spring washer, such that a component, which is fixed by means of a screw-on fastener in combination with the pre-tightening spring washer, can sufficiently compensate for the loss of displacement and / or the loss of pre-tightening force caused by a variable dynamic load to meet the sealing requirements in a high temperature and high pressure environment.

[0006] One aspect of the present invention relates to a pre-tightening spring washer, comprising an integrally formed discoidal body, the discoidal body being provided with a central hole, the discoidal body having a first contact face and a second contact face located opposite each other in a thickness direction of the discoidal body, the discoidal body being a solid of revolution formed by rotating a radial section about a central axis of rotation through 360 degrees, the central axis of rotation coinciding with a central axis of the central hole, the radial section having a first linear segment and an opposite second linear segment, the first contact face being defined by the rotation of the first linear segment, the second contact face being defined by the rotation of the second linear segment,an intermediate diameter axis being defined so that it passes through the midpoint of the second linear segment and extends normally to the second linear segment, the radial section having a mirror symmetry with respect to the intermediate diameter axis, the intermediate diameter axis not being parallel to the central axis of rotation, the first linear segment being arcuate, the concavity of the arcuate shape being oriented towards the midpoint of the second linear segment, a point of intersection of the intermediate diameter axis and the first linear segment being a point such that a vertical distance measured from this point to a segment, rectilinear line connecting the two ends of the second linear segment is the greatest of vertical distances measured from all points on the first linear segment to said rectilinear segment, the minimum thickness between the first and second contact faces of the discoid body being, in an unloaded state of the pre-tightened spring washer, greater than 3 / 4 of an unloaded height of the discoid body and greater than 1 / 12 of an unloaded outside diameter of the discoid body.

[0007] In one embodiment, the second contact face is designed such that that :

[0008] - (A) in the radial section, the second linear segment is arched, and the concavities first and second arcuate linear segments are oriented in the same direction; or

[0009] - (B) in the radial section, the second linear segment is arched, the concavities of the first and second arcuate linear segments are oriented in the same direction, a rib projects outwardly from the midpoint of the second linear segment a distance that is equal to or less than the arc height of the second linear segment in the unloaded state of the pre-tightening spring washer; or

[0010] - (C) in the radial section, the second linear segment is straight.

[0011] In one embodiment, the first contact face has a surface roughness Ra of 0.8 to 1.6.

[0012] In one embodiment, the first contact face is a face configured to contact a fastening element, and the second contact face is a face configured to contact a component to be fastened.

[0013] In one embodiment, when the pre-tightening spring washer is pre-tightened by the fastener, an axial force is exerted by the fastener on the pre-tightening spring washer, and the load-bearing portion on the first contact face swings from the innermost periphery to the outermost periphery and is finally located at the location of the first contact face farthest from the second contact face in the thickness direction.

[0014] In one embodiment, the discoid body of the pre-tightening spring washer comprises a plating consisting of a layer of nickel having a thickness greater than 3 μm.

[0015] Another aspect of the present invention relates to a method of manufacturing a pre-tightening spring washer, the method comprising: - subjecting a molten metallic material used to prepare the pre-tightening spring washer to annealing or solution annealing after forging or rolling the metallic material; - subject the metallic material to stamping using a pressing tool or turning in order to obtain a raw part for a spring washer pre-tightened leaving a margin of 0.2 to 0.5 mm; subjecting the pre-tightening spring washer blank to finish machining so that it has a surface roughness Ra of 1.6 to 3.2; using a composite pressing tool to press the pre-tightening spring washer blank in a press; subjecting the pressed pre-tightening spring washer blank to annealing and tempering, the annealing temperature being higher than 900°C and the tempering temperature being higher than 500°C; or further subjecting the pre-tightening spring washer blank to a maturing heat treatment at a maturing temperature higher than 450°C, to ensure a Rockwell hardness HRC reaching 38 to 50; forcefully press the raw part for pre-tightening spring washer at least three times at room temperature; using a shot blasting machine to harden the force-pressed pre-tightening spring washer blank or subjecting it to a maturation treatment to further increase its surface strength, a discoid body of the obtained pre-tightening spring washer having a central hole, the discoid body having a first contact face and a second contact face located opposite each other in a thickness direction of the discoid body, the discoid body being a solid of revolution formed by rotating a radial section about a central rotation axis through 360 degrees, the central rotation axis coinciding with a central axis of the central hole, the radial section having a first linear segment and an opposite second linear segment, the first contact face being defined by the rotation of the first linear segment, the second contact face being defined by the rotation of the second linear segment,an intermediate diameter axis being defined so that it passes through the midpoint of the second linear segment and extends normally to the second linear segment, the radial section having a mirror symmetry with respect to the intermediate diameter axis, the intermediate diameter axis not being parallel to the central axis of rotation, the first linear segment being arcuate, the concavity of the arcuate shape being oriented towards the midpoint of the second linear segment, a point of intersection of the intermediate diameter axis and the first linear segment being a point such that a vertical distance measured from this point to a straight segment connecting the two ends of the second linear segment is the greatest of vertical distances measured from all points on the first linear segment to said straight segment, the minimum thickness between the first and second contact faces of the body, discoid being, in an unloaded state of the pre-tightened spring washer, greater than 3 / 4 of an unloaded height of the discoid body and greater than 1 / 12 of an unloaded outside diameter of the discoid body.

[0016] In one embodiment, the method further comprises: - level the first contact face of the pre-tightening spring washer so that its surface roughness Ra reaches 0.8 to 1.6.

[0017] In one embodiment, the discoid body of the pre-tightening spring washer is provided with a plating consisting of a layer of nickel having a thickness greater than 3 μm.

[0018] Another aspect of the present invention relates to an assembly fixed by means of a pre-tightening spring washer as mentioned above, the assembly comprising: - a screw passing through a central hole of the pre-tightening spring washer; - a nut coupled to the screw and coming into contact with a first face of pre-tightening spring washer contact; and - a flange, the screw being adapted to pass through the flange and the flange being adapted to contact a second face of the pre-tightening spring washer, and an axial pre-tightening force being exerted by the nut on the pre-tightening spring washer such that the pre-tightening spring washer is maintained in its pre-tightened state.

[0019] By using the technical means of the present invention, the spring washer is designed such that, when the already fixed component experiences a variable dynamic load, the spring washer has a higher pre-tightening capacity, a better force compensation capacity and a better displacement compensation capacity; and, on the other hand, the spring washer can provide secondary fixation and compensation for the already fixed component to ensure a secure fixation strength, and thus a durable and reliable connection safety. Furthermore, by using the technical means of the present invention, a reduction in the strength of the pre-tightening spring washer caused by stress concentration during fixation can be avoided. Furthermore, the pre-tightening spring washer according to the present invention is particularly suitable for high-temperature and high-corrosive operating conditions.

[0020] By using the technical means of the present invention, with the deliberate design of a relationship between the minimum thickness, the unloaded height and the unloaded outer diameter of the body of the pre-tightening spring washer, the spring washer will have a higher pre-tightening capacity, a better force compensation capacity and a better displacement compensation capacity; and will provide secondary support and compensation by maintaining a safe strength. Furthermore, according to the present invention, the radial section is designed to avoid a problem of reduction of the resistance of the pre-tightening spring washer caused by stress concentration or similar. Brief description of the drawings

[0021] The principle and other aspects of the present invention will be better understood from the following description, in combination with the drawings. It should be noted that, although the drawings may be presented in different ratios for the sake of clarity, this should not affect the understanding of the present invention. In the drawings:

[0022] [Fig-1] [Fig.l] is a top view schematically illustrating a washer pre-tightening spring according to one embodiment of the present invention;

[0023] [Fig.2] [Fig.2] is a sectional view schematically illustrating the pre-tightening spring washer according to the embodiment of the present invention, said sectional view being taken along an imaginary sectional plane passing through a central axis of rotation of the pre-tightening spring washer;

[0024] [Fig.3] [Fig.3] is a sectional view schematically illustrating a washer pre-tightening spring according to another embodiment of the present invention, said sectional view being taken along an imaginary sectional plane passing through a central axis of rotation of the pre-tightening spring washer;

[0025] [Fig.4] [Fig.4] is a sectional view schematically illustrating a washer pre-tightening spring according to another embodiment of the present invention, said sectional view being taken along an imaginary sectional plane passing through a central axis of rotation of the pre-tightening spring washer;

[0026] [Fig.5A] [Fig.5A] is one of sectional views schematically illustrating possible arrangements, respectively, of pre-tightening spring washers according to the embodiments of the present invention;

[0027] [Fig.5B] [Fig.5B] is one of sectional views schematically illustrating possible arrangements, respectively, of pre-tightening spring washers according to the embodiments of the present invention;

[0028] [Fig.5C] [Fig.5C] is one of sectional views schematically illustrating possible arrangements, respectively, of pre-tightening spring washers according to the embodiments of the present invention;

[0029] [Fig.6] [Fig.6] is a sectional view schematically illustrating the use of the pre-tightening spring washer of the embodiment shown in [Fig.2] for securing a component;

[0030] [Fig.7] [Fig.7] is a sectional view schematically illustrating the use of the pre-tightening spring washer of the embodiment shown in [Fig.3] for securing a component;

[0031] [Fig.8] [Fig.8] is a sectional view schematically illustrating the use of the pre-tightening spring washer of the embodiment shown in [Fig.4] for securing a component;

[0032] [Fig.9] [Fig.9] is a curve graph schematically illustrating a relationship between force and displacement for the pre-tightening spring washer of the embodiment shown in [Fig.3];

[0033] [Fig. 10] [Fig. 10] is a curve graph schematically illustrating a force-displacement relationship for the pre-tightening spring washer of the embodiment shown in [Fig.2]; and

[0034] [Fig. 11] [Fig. 11] is a flowchart schematically illustrating a method, according to one embodiment of the present invention, for manufacturing the pre-tightening spring washer. Methods of implementation

[0035] In the drawings of the present invention, elements having the same configuration or having a similar function are respectively designated by the same reference numerals.

[0036] [Fig.l] is a top view schematically illustrating a pre-tightening spring washer 100 according to an embodiment of the present invention. The pre-tightening spring washer 100 comprises a spring washer body 1 formed integrally. The spring washer body 1 is a substantially discoidal body having a central hole 20. The spring washer body 1 is therefore designed in the form of a solid of revolution about a central axis O thereof. The central hole 20 is designed such that a fastener such as a screw can pass through the central hole 20. The discoidal body of the spring washer body 1 has two contact faces located substantially opposite each other along a thickness direction thereof.The contact faces are designed such that one of them is adapted to come into contact with a corresponding fastening element such as a nut, and the other is adapted to come into contact with a component to be fastened. According to a technical solution of the present invention, at least the contact face coming into contact with the nut is arcuate.

[0037] [Fig.2] is a sectional view schematically illustrating a spring washer pre-tightening 110 according to a first embodiment of the present invention. The sectional view is taken along an imaginary sectional plane passing through a central axis of rotation O of the pre-tightening spring washer 110. If a body of the pre-tightening spring washer is considered as a solid of revolution about the central axis of rotation O, the solid of revolution can be formed by rotating a section SI 10 shown in [Fig. 2] about the central axis of rotation O through 360 degrees. It will be understood that, in the context of the present invention, the section (e.g., section SI 10 shown in [Fig. 2]) of the body of the pre-tightening spring washer can be called a radial section. This radial section is a section taken radially from the central axis of rotation O of the body of the pre-tightening spring washer. This section lies in a plane passing through the central axis of rotation O. This section, after a rotation around the central axis of rotation O through 180 degrees, coincides with another radial section (for example, a radial section SI 10' shown in [Fig.2]) of the body of the same pre-tightening spring washer. Therefore, there is, between the two radial sections, a mirror symmetry with respect to the central axis of rotation O.

[0038] In [Fig.2], the radial section SI 10 is shown with four angles A, B, C and D. A first contact face 111 of the body of the pre-tightening spring washer 110 is formed by rotating a linear segment between the angles A and B, around the central axis of rotation O, through 360 degrees. A second contact face 112 of the body of the pre-tightening spring washer 110 is formed by rotating a linear segment between the angles C and D, around the central axis of rotation O, through 360 degrees. An inner wall of the central hole of the body of the pre-tightening spring washer 110 is formed by rotating a linear segment between the angles B and C, around the central axis of rotation O, through 360 degrees. A peripheral face of the body of the pre-tightening spring washer 110 is formed by rotating a linear segment between the angles A and D, around the central axis of rotation O, through 360 degrees.The first contact face 111 and the second contact face 112 are located opposite each other substantially in the thickness direction of the body of the pre-tightening spring washer 110. Here, the first contact face 111 is a face designed to contact a nut, and the second contact face 112 is a face designed to contact a component to be fixed.

[0039] According to the first embodiment shown in [Fig. 2], in the radial section SI 10, the linear segment between angles A and B is designed to be arcuate or cambered or substantially arcuate or substantially cambered, and the linear segment between angles C and D is designed to be straight or substantially straight. In particular, the concavity of the arcuate or cambered or substantially arcuate or substantially cambered linear segment between angles A and B is oriented in the direction of the linear segment or the midpoint of the linear segment between angles C and D, i.e., the point on the linear segment between angles A and B, as the midpoint between angles A and B is approached, becomes increasingly distant from the linear segment between angles C and D.In the radial section SI 10, an axis M or an axis of intermediate diameter M is defined so that it passes through the midpoint of the straight segment between the angles C and D perpendicularly or normally to said straight segment. In an unloaded state of the pre-tightening spring washer 110 (no axial force exerted by the respective fastening element acting on the spring washer in said unloaded state. load), when the pre-tightening spring washer 110 is placed on a horizontal plane such that the second contact face 112 is facing downwards, the second contact face 112 of the pre-tightening spring washer 110 contacts the horizontal plane with its outermost radial periphery (corresponding to the angle D shown in [Fig. 2]). In a loaded state of the pre-tightening spring washer 110 (an axial force exerted by the nut on the first contact face 111 being oriented along a direction from the first contact face 111 to the second contact face 112 in said loaded state), as the exerted axial force increases, the second contact face 112 of the spring washer 110 contacts a plane of the component to be fixed both with its innermost radial periphery (corresponding to the angle C shown in [Fig.2]) and with its outermost radial periphery (corresponding to the angle D shown in [Fig.2]). The state in which the pre-tightening spring washer 110 is then found can be called a flattening state and, on the other hand, a load supported by the pre-tightening spring washer 110 between the nut and the plane of the component to be fixed can be called a flattening load. In the flattening state, the pre-tightening spring washer 110 cannot provide displacement compensation but said pre-tightening spring washer 110 can provide force compensation. It will be understood that, in the unloaded state of the pre-tightening spring washer 110, the intermediate diameter axis is not parallel or substantially not parallel to the central axis of rotation in the plane of the radial section.

[0040] When applying an axial tightening force to the pre-tightening spring washer 110, the nut will first come into contact with the innermost periphery of the first contact face 111 (corresponding to the angle B shown in [Fig. 2]), i.e., the axial load-bearing point or portion is initially at the innermost periphery. Subsequently, as the axial force increases, the axial load-bearing point or portion on the first contact face 111, due to the first contact face 111 being curved or cambered, will tilt from the innermost periphery to the outermost periphery.According to one embodiment of the present invention, the body of the pre-tightening spring washer 110 is configured such that, when the pre-tightening spring washer 110 is in its pre-tightening state, the curved or cambered first contact face 111 will enable concentration of the axial load-bearing point or portion mainly on a portion of the curved or cambered first contact face 111 located farthest from the second contact face 112 along a thickness direction of the pre-tightening spring washer 110. To ensure that the axial force in the pre-tightening state can be distributed more evenly on the second contact face 112 to improve the pre-tightening capability of the spring washer. According to an embodiment of the present invention, in the radial section SI 10, the thickness of the body of the pre-tightening spring washer 110 gradually decreases or decreases from the intermediate diameter axis M respectively toward a peripheral face of the body of the pre-tightening spring washer 110 and toward an inner wall of the central hole of the body of the pre-tightening spring washer 110. In other words, a point of intersection of the intermediate diameter axis M and the line segment between angles A and B is a point on the line segment between angles A and B such that a vertical distance measured from this point to a straight line segment between angles C and D is the largest of vertical distances measured from all points on the line segment between angles A and B to the straight line segment between angles C and D.

[0041] In a preferred embodiment, the angles B and D of the radial section SI 10 are respectively rounded angles so that, when the body of the pre-tightening spring washer 110 is formed by rotating the radial section SI 10 about the central rotation axis O by 360 degrees, smooth transition portions are formed respectively between the second contact face 112 of the body of the pre-tightening spring washer 110 and the inner wall of the central hole and between the second contact face 112 of the body of the pre-tightening spring washer 110 and the peripheral face by these rounded angles, in order to improve the continuity and uniformity of force application during fastening. In the context of the present invention, with respect to the thickness of the body of the pre-tightening spring washer 110, these rounded corners or the smooth transition portions formed by the rotation of these rounded corners may be omitted.Furthermore, when it is desirable to determine the thickness of the body of the pre-tightening spring washer 110 at a location of said body, a straight distance measured from a point on the second contact face 112, corresponding to the location, along the normal direction of the point to another corresponding point of the first contact face 111 is considered to be the thickness of the body of the pre-tightening spring washer 110 at the location of said body.

[0042] When, in an unloaded state, the pre-tightening spring washer 110 is placed on a horizontal plane with its second contact face 112 facing downward, a height H measured in the direction of gravity from the horizontal plane to the highest point of the first contact face 111 may be referred to as the unloaded height of the body of the pre-tightening spring washer 110; on the other hand, the outermost diameter of the body of the pre-tightening spring washer 110 may be referred to as the unloaded diameter of the body of the pre-tightening spring washer 110, and the outermost radius of the body of the pre-tightening spring washer 110 may be referred to as the unloaded radius of the body of the pre-tightening spring washer 110.

[0043] According to a preferred embodiment of the present invention, the spring washer pre-tightening spring washer 110 may be designed such that the minimum thickness of the body of the pre-tightening spring washer 110 is greater than 3 / 4 of the unloaded height of the body of the pre-tightening spring washer 110 and greater than 1 / 12 of the unloaded diameter (or outside diameter) of the body of the pre-tightening spring washer 110. Unlike a conventional spring washer which is formed with a small thickness and pre-tightened with a smaller force, the spring washer according to the present invention may be formed with a larger thickness and pre-tightened with a larger force.

[0044] [Fig. 6] schematically illustrates the fixing of a component by means of a pre-tightening spring washer 110 according to the first embodiment shown in [Fig. 2]. In the context of the present invention, the component to be fixed can be any element in the mechanical field that needs to be fixed. In [Fig.6], two flanges which are used to couple pipelines (not shown) in chemical manufacturing equipment are designated by a reference numeral "2"; a washer or sealing washer which is placed between the two flanges 2 to provide a fluid seal therebetween is designated by a reference numeral "3"; a screw which passes through the center holes of two aligned pre-tightening spring washers 110 and the aligned holes of the two flanges is designated by a reference numeral "5"; nuts, which are respectively screwed onto both ends of a screw to exert an axial pre-tightening force on the pre-tightening spring washer 110 and the flanges are respectively designated by a reference numeral "4".A person skilled in the art will understand that, in the embodiment in which the flanges are coupled, each flange may be provided with a plurality of through holes, and a plurality of screws are then respectively arranged to pass through the through holes. Each of the plurality of screws is provided with one or more pre-tightening spring washers according to the present invention such that the spring washer(s) may be pre-tightened by screwing nuts onto the screw. It will be understood that Figs. 6, 7 and 8 illustrate only a portion of the flanges adjacent to a through hole.

[0045] As mentioned above, as the nuts 4 are screwed in, the pre-tightening spring washers 110 will be in the pre-tightening state (for the design of the pre-tightening spring washer 100, its flattened state may constitute its pre-tightening state), so that sufficient pre-tightening force can be exerted between the flanges 2 to ensure fluid tightness between the pipes. Due to variations in the fluid pressure, a constant axial alternating force will act on the flanges 2. Since the first contact face 111 of the pre-tightening spring washer 110 according to the present invention is designed such that it is curved or cambered, force compensation for the constant axial alternating force can be achieved so that the sealing washer 3 can be held with adequate pressure between the flanges 2 to ensure a reliable fluid-tight connection.

[0046] In a preferred embodiment, in order to ensure that the pre-tightening spring washers can be used in corrosion-resistant flange connection situations, the body of the pre-tightening spring washer may be provided with a plating consisting of a layer of nickel on its surface. The nickel layer may have a thickness greater than 3 μm (micrometers).

[0047] [Fig. 3] is a sectional view schematically illustrating a pre-tightening spring washer 120 according to a second embodiment of the present invention, said sectional view being taken along a section passing through a central rotation axis O of the pre-tightening spring washer 120. In the embodiment shown in [Fig. 3], a body of the pre-tightening spring washer 120 can be considered to be formed by rotating a radial section S120 about the central rotation axis O of the body of the pre-tightening spring washer 120 through 360 degrees. Although the radial section S120 is also shown with four angles A, B, C and D, the radial section S120 is different from the embodiment shown in [Fig. 2] in that a linear segment between the angles C and D is arcuate or cambered.That is, both a first contact face 121 and a second contact face 122 of the pre-tightening spring washer body 120 that are located opposite each other along a thickness direction thereof are curved or cambered. In the radial section S120, the concavities of the arcuate or cambered line segment between angles A and B and the arcuate or cambered line segment between angles C and D are oriented in the same direction, and the concavity of the arcuate or cambered line segment between angles A and B faces the line segment or the midpoint of the line segment between angles C and D.In a preferred embodiment, the linear segment between angles A and B of the radial section S120 is arcuate such that the curvature of the linear segment is the same as the curvature of the linear segment between angles C and D of the radial section S120 and / or the center of curvature of the linear segment coincides with the center of curvature of the linear segment between angles C and D of the radial section S120.

[0048] In the radial section S120, an axis of intermediate diameter M is defined such that it passes through the midpoint of the arcuate or cambered linear segment between angles C and D normal to the linear segment. In an unloaded state of the pre-tightening spring washer 120, in the radial section S120, a point of intersection of the axis of intermediate diameter M and the linear segment between angles A and B is a point on the linear segment between angles A and B such that a vertical distance measured from this point to a straight segment (if any) between angles C and D is the greatest of vertical distances measured from all points on the segment linear between angles A and B to the straight segment between angles C and D. For the sake of simplification, an explanation of an unloaded height and an unloaded radius of the pre-tightening spring washer 120 will be omitted since reference may be made to the definitions given for the embodiment shown in [Fig. 2]. In a preferred embodiment, in order to ensure that unimpeded movement of the load-bearing point is possible as desired when the spring washer is pre-tightened and / or when displacement compensation is performed by the pre-tightening spring washer 120, the first contact face of the pre-tightening spring washer is formed to be a smooth face, having a surface roughness Ra of 0.8 to 0.6.

[0049] According to a preferred embodiment of the present invention, the pre-tightening spring washer 120 may be designed such that the minimum thickness of the body of the pre-tightening spring washer 120 is greater than 3 / 4 of the unloaded height of the body of the pre-tightening spring washer 120 and greater than 1 / 12 of the unloaded diameter of the body of the pre-tightening spring washer 120. Unlike a conventional spring washer which is formed with a small thickness and pre-tightened with a smaller force, the spring washer according to the present invention may be formed with a larger thickness and pre-tightened with a larger force.

[0050] The body of the pre-tightening spring washer 120 is designed such that as an axial pre-tightening force is exerted on the pre-tightening spring washer 120 by screwing the nuts, the second contact face 122 of the pre-tightening spring washer 120, in its pre-tightened state, will contact a planar surface of a component to be fixed with both the innermost radial periphery (corresponding to the angle C shown in [Fig. 3]) of the second contact face and the outermost radial periphery (corresponding to the angle D shown in [Fig. 3]) of the second contact face. In the pre-tightened state, the second contact face 122 of the pre-tightening spring washer 120 does not fully contact the flat surface of the component due to the curved or cambered shape of the second contact face.Therefore, when an alternating force is applied to the component, the pre-tightening spring washer 120 will be able to provide not only force compensation but also displacement compensation for the fixed component.

[0051] [Fig. 7] schematically illustrates the fixing of flanges 2 by means of pre-tightening spring washers 120 according to the second embodiment shown in [Fig. 3]. With regard to [Fig. 7], for the sake of simplification, the elements designated by the same reference numbers as in [Fig. 6] will be omitted hereinafter, since reference can be made to the explanations given for [Fig. 6]. It can be seen that, when the pre-tightening spring washers 120 are in their state of pre-tightening, the second contact faces 122 of the pre-tightening spring washers 120 are in contact with the respective flanges 2, respectively with both the innermost radial periphery and the outermost radial periphery of the second contact faces. However, due to the curved or cambered shape of the second contact faces 122, there remains a portion, located between the innermost radial periphery and the outermost radial periphery of the second contact faces, which is not in contact with the respective flanges 2. When the alternating force is applied to the flanges 2 by a pressurized fluid, the force acting between the flanges 2 will change and a minor relative displacement change may take place between the flanges 2.With the pre-tightening spring washer(s) 120 according to the present invention, both force compensation and displacement compensation can be achieved, so that the two flanges 2 can be held together with sufficient and uniform pre-tightening force and the sealing washer 3 can be pressed adequately to ensure a reliable fluid-tight connection.

[0052] [Fig. 4] is a sectional view schematically illustrating a pre-tightening spring washer 130 according to a third embodiment of the present invention, said sectional view being taken along a section passing through a central rotation axis O of the pre-tightening spring washer 130. The embodiment shown in [Fig. 4] is different from the embodiment shown in [Fig. 3] in that a second contact face 132 of a body of the pre-tightening spring washer 130 is formed to include an annular rib 133. Therefore, for the sake of simplification, except for the annular rib 133, the explanation of the other elements of the pre-tightening spring washer 130 will be omitted hereinafter since reference may be made to the explanations given for the second embodiment shown in [Fig. 3] or its variations.

[0053] In a radial section S130 of the pre-tightening spring washer 130, four angles A, B, C and D are shown. A linear segment between angles A and B and / or a linear segment between angles C and D is arcuate or cambered. In the radial section S130, the rib 133 projects outward from the linear segment between angles C and D along an axis of intermediate diameter M. The rib 133 projects outward from the linear segment between angles C and D by a distance that is not greater than the arc height or camber height of the arcuate or cambered linear segment between angles C and D in an unloaded state of the pre-tightening spring washer 130.

[0054] According to a preferred embodiment of the present invention, the pre-tightening spring washer 130 may be designed such that the minimum thickness of the body of the pre-tightening spring washer 130 is greater than 3 / 4 of the unloaded height of the body of the pre-tightening spring washer 130 and greater than 1 / 12 of the diameter (or outer diameter) without load of the body of the pre-tightening spring washer 130. Unlike a conventional spring washer which is formed with a small thickness and pre-tightened with a lesser force, the spring washer according to the present invention can be formed with a larger thickness and pre-tightened with a greater force.

[0055] The body of the pre-tightening spring washer 130 is designed such that as an axial pre-tightening force is exerted on the pre-tightening spring washer 130 by screwing the nuts, the second contact face 132 of the pre-tightening spring washer 130, in its pre-tightened state, will contact a planar surface of a component to be fixed with both the innermost radial periphery (corresponding to the angle C shown in [Fig. 4]) of the second contact face and the outermost radial periphery (corresponding to the angle D shown in [Fig. 4]) of the second contact face. The annular rib 133 may then or may not contact the planar surface of the component. Therefore, compared to the force compensation and displacement compensation provided by the embodiment shown in [Fig.3], the presence of the annular rib 133 can ensure greater force compensation.

[0056] [Fig. 8] schematically illustrates the fixing of flanges 2 by means of pre-tightening spring washers 130 according to the third embodiment shown in [Fig. 4]. It can be seen that, when the pre-tightening spring washers 130 are in their pre-tightening state, the second contact faces 132 of the pre-tightening spring washers 130 are in contact with the respective flanges 2, respectively with both the innermost radial periphery and the outermost radial periphery of the second contact faces. On the other hand, the annular ribs 133 respectively come into contact with the flanges 2 in a non-load-bearing manner or do not come into contact with the flanges 2.In this case, when an alternating force is applied to the flanges 2 by a fluid supplied in the pipelines with a pressure variation, the pre-tightening spring washers 130 according to the present invention can ensure both force compensation and displacement compensation in the presence of a sufficient pre-tightening force. Thus, the sealing washer 3 can be adequately pressed to ensure a reliable fluid-tight connection. Furthermore, since the annular ribs 133 will contact the flanges 2 when the alternating force is applied to the pre-tightening spring washers 130, the time required for the pre-tightening spring washers 130 to fully contact the flanges 2 can be shortened and the contact area therebetween can be enlarged, resulting in an increased force compensation capability.

[0057] Those skilled in the art will understand that, in another embodiment, two or more annular ribs, concentric with each other, may be formed in the second contact face 132 of the pre-tightening spring washer 130 as long as these ribs, in a view corresponding to the radial section S130, protrude outwardly from the linear segment between the angles C and D by a distance which is not greater than the arc height or camber height of the arcuate or cambered linear segment between the angles C and D in the unloaded state of the pre-tightening spring washer 130. For example, in the case in which two annular ribs, concentric with each other, are formed, in a view corresponding to the radial section S130, the vertical distances of the two ribs measured from the intermediate diameter axis M are identical to each other.

[0058] In order to explain the advantages of the technical solutions of the present invention, Table 1 indicates the flattening load results obtained in tests carried out for spring washers designed according to the prior art and spring washers designed according to the present invention. [Tables 1] Test No. State without load State of flattening Explanation Outer diameter (mm) Inside diameter (mm) Minimum thickness (mm) Height without load (mm) Minimum thickness / hour without load = RI Minimum thickness / outer diameter without load = R2 Flattening load (kN) Previous tec hnique 1 31.56 16.46 1.8 2.58 0.7 0.06 9.67 RI <3 / 4 and R2 < 1 / 12 2 44.86 22.52 2.52 3.64 0.69 0.06 12.47 RI < 3 / 4 and R2 < 1 / 12 3 45.92 31.9 2.54 3.78 0.67 0.06 17.67 RI <3 / 4 and R2 < 1 / 12 4 35.5 18.3 2 2.8 0.71 0.06 9.69 RI <3 / 4 and R2 < 1 / 12 Technical solutions of the present invention 5 45.3 22 5 5.68 0.88 0.11 138.79 RI >3 / 4 and R2 > 1 / 12 6 90.4 45.82 7.96 9.2 0.87 0.09 322.77 RI >3 / 4 and R2 > 1 / 12 7 40.32 23.14 7.4 7.8 0.95 0.18 125.17 RI >3 / 4 and R2 > 1 / 12 8 50.68 30.88 7.4 9.44 0.78 0.15 218.27 RI >3 / 4 and R2 > 1 / 12 9 43.16 25.1 3.9 4.5 0.87 0.09 43.34 RI >3 / 4 and R2 > 1 / 12 10 53.78 31.1 4.86 5.66 0.85 0.09 68.49 RI >3 / 4 and R2 > 1 / 12 11 52.8 30.9 5 5,65 0.88 0.09 219.3 RI >3 / 4 and R2 > 1 / 12 12 52.8 30.9 5 5.64 0.88 0.09 49.8 RI >3 / 4 and R2 > 1 / 12,

[0059] In Table 1, the flattening loads were tested for different sizes of pre-tightening spring washers. Tests (1) to (4) were carried out for the prior art pre-tightening spring washers (the thickness minimum thickness of the pre-tightening spring washers is not more than 3 / 4 of the unloaded height and not more than 1 / 12 of the unloaded outer diameter). Tests (5) to (12) were carried out for the pre-tightening spring washers designed according to the present invention (the minimum thickness of the pre-tightening spring washers is more than 3 / 4 of the unloaded height and more than 1 / 12 of the unloaded outer diameter). It should be noted here that a flattened state of the pre-tightening spring washer corresponds to a state in which the second contact face of the pre-tightening spring washer is in complete contact with a component to be fixed, such that no axial displacement will take place between the pre-tightening spring washer and the component. The flattening load corresponds to a load supported by the pre-tightening spring washer in the flattened state.

[0060] By comparing the flattening load results measured in the tests, it can be seen that the flattening loads of the pre-tightening spring washers designed according to the present invention appear to be higher than the flattening loads of the prior art pre-tightening spring washers. In other words, in the presence of the same alternating force, the component can be pre-tightened more reliably by the pre-tightening spring washers designed according to the present invention. In particular, by comparing the results of Test (2), Test (5) and Test (9), it can be seen that, when the difference between the outer diameter and the inner diameter of a pre-tightening spring washer is not excessive, adjusting RI and R2 by changing the minimum thickness and the no-load height can significantly increase the flattening load.

[0061] In Table 1, Test (11) was carried out for a pre-tightening spring washer designed according to the second embodiment shown in [Fig. 3], and Test (12) was carried out for a pre-tightening spring washer designed according to the first embodiment shown in [Fig. 2]. The two pre-tightening spring washers have the same inner and outer diameters, the same minimum thickness, and slightly different unloaded heights, respectively. [Fig. 9] shows a force / displacement curve of Test (11), and [Fig. 10] shows a force / displacement curve of Test (12).By comparing the two curves, it can be seen that when both the first and second contact faces of a pre-tightening spring washer are designed to be curved or cambered, the flattening load of said pre-tightening spring washer is substantially greater than the flattening load of the other pre-tightening spring washer whose first contact face is designed to be curved or cambered and whose second contact face is flat. Furthermore, once the flattening load is reached, the displacement of said pre-tightening spring washer is substantially greater than that of the other pre-tightening spring washer. It can be thought that when a pre-tightening spring washer . clamping having a size equal to or similar to that of the pre-tightening spring washer of Test (11) is formed to have an annular rib, as in the third embodiment shown in [Fig.4], in a body of the pre-tightening spring washer, the flattening load of the pre-tightening spring washer formed to have the annular rib will be greater than the flattening load of Test (11); however, the displacement of this pre-tightening spring washer, when the flattening load is reached, will be less than the displacement of Test (11) and greater than the displacement of Test (12).

[0062] [Fig. 11] is a flowchart schematically illustrating a method, according to one embodiment of the present invention, for manufacturing a pre-tightening spring washer of the present invention. First, in Step S10, a molten metal material for preparing the pre-tightening spring washer is forged or rolled and, then, is subjected to annealing or solution annealing, the molten metal material for preparing the pre-tightening spring washer being selected from a group consisting of spring steel, stainless steel, and a nickel-based alloy. In Step S20, a blank for a pre-tightening spring washer is obtained by stamping using a pressing tool or turning from the metal material, leaving a margin of 0.2 to 0.5 mm (millimeter).In Step S30, the blank for pre-tightening spring washer is subjected to finish machining such that it has a surface roughness Ra of 1.6 to 3.2. In Step S40, in a press, the blank for pre-tightening spring washer is pressed using a composite pressing tool. In Step S50, the blank for pre-tightening spring washer is preheated according to the material characteristics of the selected metal material, and then is subjected to annealing (the annealing temperature being higher than 900°C) and tempering (the tempering temperature being higher than 500°C) or, further, is subjected to a maturing heat treatment at a maturing temperature higher than 450°C, to ensure a Rockwell hardness HRC reaching 38 to 50. In Step S60, the blank for pre-tightening spring washer is force-pressed.For example, a single blank for a pre-tightening spring washer may be force-pressed by the press at least three times at room temperature. In Step S70, the force-pressed blank for a pre-tightening spring washer is hardened by means of a shot blasting machine or subjected to a maturing treatment to further increase its surface strength. In Step S80, a first contact face of the pre-tightening spring washer is leveled so that the surface roughness Ra reaches 0.8 to 1.6. Optionally, in Step S90, the pre-tightening spring washer is provided with a plating consisting of a nickel layer on its surface. For example, after de-oiling, washing, and cleaning the surface of the pre-tightening spring washer, it is subjected to electrolytic nickel plating or electroless nickel plating so that the . The nickel layer of the pre-tightening spring washer has a thickness greater than 3 μm.

[0063] Although in the embodiments shown in [Fig. 7] to 9, only one pre-tightening spring washer is used on one side of a flange 2, those skilled in the art will appreciate that several pre-tightening spring washers according to the present invention may be superimposed on one another. Possible arrangements of the pre-tightening spring washers in which they are superimposed on one another include, but are not limited to, the arrangements shown in [Fig. 5A] to 5C.

[0064] Although specific embodiments of the present invention have been explained in detail, these are for illustrative purposes only and should not be construed as limiting the scope of the present invention in any way. Furthermore, those skilled in the art will understand that the embodiments described herein may be arbitrarily combined with each other. Without departing from the spirit and scope of the present invention, various substitutions, modifications, and changes may be contemplated.

Claims

Claims

1. A pre-tightening spring washer, comprising an integrally formed discoid body, the discoid body being provided with a central hole, the discoid body having a first contact face and a second contact face located opposite each other in a thickness direction of the discoid body, the discoid body being a solid of revolution formed by rotating a radial section about a central rotation axis through 360 degrees, the central rotation axis coinciding with a central axis of the central hole, the radial section having a first linear segment and an opposing second linear segment, the first contact face being defined by the rotation of the first linear segment, the second contact face being defined by the rotation of the second linear segment, an intermediate diameter axis being defined so that it passes through the midpoint of the second linear segment and extends normally to the second linear segment,the radial section having a mirror symmetry with respect to the intermediate diameter axis, the intermediate diameter axis not being parallel to the central axis of rotation, the first linear segment being arcuate, the concavity of the arcuate shape being oriented towards the midpoint of the second linear segment, a point of intersection of the intermediate diameter axis and the first linear segment being a point such that a vertical distance measured from this point to a straight segment connecting the two ends of the second linear segment is the greatest of vertical distances measured from all points on the first linear segment to said straight segment, - the minimum thickness between the first and second contact faces of the discoid body being, in an unloaded state of the pre-tightening spring washer,greater than 3 / 4 of an unloaded height of the discoid body and greater than 1 / 12 of an unloaded outside diameter of the discoid body.,

2. A pre-tightening spring washer according to claim 1, wherein the second contact face is designed such that: (A) in the radial section, the second linear segment is arcuate, and the concavities of the first and second arcuate linear segments are oriented in the same direction; or (B) in the radial section, the second linear segment is arcuate, the concavities of the first and second arcuate linear segments are oriented in the same direction, a rib projects outwardly from the midpoint of the second linear segment for a distance that is equal to or less than the arc height of the second linear segment in the unloaded state of the pre-tightening spring washer; or (C) in the radial section, the second linear segment is straight.

3. A pre-tightening spring washer according to claim 1 or 2, wherein the first contact face has a surface roughness Ra of 0.8 to 1.

6.

4. A pre-tightening spring washer according to claim 3, wherein the first contact face is a face adapted to contact a fastener, and the second contact face is a face adapted to contact a component to be fastened.

5. The pre-tightening spring washer according to claim 4, wherein when the pre-tightening spring washer is pre-tightened by the fastener, an axial force is exerted by the fastener on the pre-tightening spring washer, and the load-bearing portion on the first contact face swings from the innermost periphery to the outermost periphery and is finally located at the location of the first contact face farthest from the second contact face in the thickness direction.

6. A pre-tightening spring washer according to claim 5, wherein the discoid body of the pre-tightening spring washer is provided with a plating consisting of a nickel layer having a thickness greater than 3 pm.

7. A method of manufacturing a pre-tightening spring washer, comprising: - subjecting a molten metal material for preparing the pre-tightening spring washer to annealing or solution annealing after forging or rolling the metal material; - subjecting the metal material to stamping by means of a pressing tool or turning to obtain a blank for a pre-tightening spring washer with a margin of 0.2 to 0.5 mm; - subjecting the blank for a pre-tightening spring washer to finishing machining such that it has a surface roughness Ra of 1.6 to 3.2; using a composite pressing tool to press the pre-tightening spring washer blank in a press; subjecting the pressed pre-tightening spring washer blank to annealing and tempering, the annealing temperature being higher than 900°C and the tempering temperature being higher than 500°C; or further subjecting the pre-tightening spring washer blank to a maturing heat treatment at a maturing temperature higher than 450°C, to ensure a Rockwell hardness HRC reaching 38 to 50; force-pressing the pre-tightening spring washer blank at least three times at room temperature; using a shot blasting machine to harden the force-pressed pre-tightening spring washer blank or subjecting it to a maturation treatment to further increase its surface strength, a discoid body of the obtained pre-tightening spring washer having a central hole, the discoid body having a first contact face and a second contact face located opposite each other in a thickness direction of the discoid body, the discoid body being a solid of revolution formed by rotating a radial section about a central rotation axis through 360 degrees, the central rotation axis coinciding with a central axis of the central hole, the radial section having a first linear segment and an opposite second linear segment, the first contact face being defined by the rotation of the first linear segment, the second contact face being defined by the rotation of the second linear segment,an intermediate diameter axis being defined so that it passes through the midpoint of the second linear segment and extends normally to the second linear segment, the radial section having a mirror symmetry with respect to the intermediate diameter axis, the intermediate diameter axis not being parallel to the central axis of rotation, the first linear segment being arcuate, the concavity of the arcuate shape being oriented towards the midpoint of the second linear segment, a point of intersection of the inter-diameter axis, median and of the first linear segment being a point such that a vertical distance measured from this point to a rectilinear segment connecting the two ends of the second linear segment is the greatest of vertical distances measured from all points on the first linear segment to said rectilinear segment, - the minimum thickness between the first and second contact faces of the discoid body being, in an unloaded state of the pre-tightened spring washer, greater than 3 / 4 of an unloaded height of the discoid body and greater than 1 / 12 of an unloaded outside diameter of the discoid body.

8. Method according to claim 7, further comprising: - leveling the first contact face of the pre-tightening spring washer such that its surface roughness Ra reaches 0.8 to 1.

6.

9. A method according to claim 7 or 8, wherein the discoid body of the pre-tightening spring washer is provided with a plating consisting of a nickel layer having a thickness greater than 3 pm.

10. An assembly secured by means of a pre-tightening spring washer according to any one of claims 1 to 6, the assembly comprising: - a screw passing through a central hole of the pre-tightening spring washer; - a nut coupled to the screw and contacting a first contact face of the pre-tightening spring washer; and - a flange, the screw being adapted to pass through the flange and the flange being adapted to contact a second face of the pre-tightening spring washer, and an axial pre-tightening force being exerted by the nut on the pre-tightening spring washer such that the pre-tightening spring washer is maintained in its pre-tightened state.

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