JP2011117504A - E-ext lock bolt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent the looseness by singly using a bolt and also apply the looseness prevention technology to looseness prevention of a nut. <P>SOLUTION: An insertion hole having a diameter equivalent to approximately 0.3 times of 'nominal size' is bored in a center axis of a male screw tip of a conventional bolt in a depth with a dimension equivalent to approximately 0.8 times thereof. 'A straight line groove' having a groove width size of 0.7-1.6 mm is processed in the same depth as the insertion hole. In the 'straight line groove' of the slot, 'an E-shaped snap ring' in JIS specification is angularly shaped. 'A specially manufactured E-shaped snap ring' of a shape containing a 'crest bending' or 'semicircular bending' part mutually fitted is inserted in and suitable for the insertion hole in a back part side surface on an opposite side to an opening in the snap ring. When the bolt is fastened to the mating female screw, the outer edge of the bolt pressed onto the inner diameter of a female screw to be locked by preload in an axially orthogonal direction through elastic expanding force of bending of the 'specially manufactured E-shaped snap ring' , wherein the rotation of the bolt is prevented through the medium of the slot at the tip of the male screw to prevent the looseness of the bolt. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to prevention of loosening of a bolt and prevention of loosening of a nut that is screwed into a bolt when a bolt alone is used to fasten a member to be fastened to a mating female screw member when no nut is used.

When a conventional bolt is used in combination with a locking nut, it is not necessary to provide a “locking” to the bolt itself. On the other hand, when fastening a fastened member to a mating female screw member with a bolt alone, use a hexagon bolt with a flange for the purpose of preventing “sagging and loosening” for the soft fastened member, or contact with the fastened member A large flat washer is used together. However, it cannot be said that it is an effective means for preventing the bolt from rotating against the sliding of the contact surface between the bottom surface of the bolt head and the fastening member caused by an external force such as vibration.
"Screw story", Yamamoto Atsushi Japanese Standards Association pp. 73-75

A “spring washer” is used as a locking member for hard members to be fastened. However, especially in nuts where locking is considered a problem, the results of the "right-angle screw loosening test" show not only a locking effect but also a locking effect compared to when no spring washer is used. I know it ’s inferior. In addition, the experimental results of the “right angle shaft screw loosening test” also show that a kind of locking nut, a pre-ringing torque hex nut with a nylon insert, has no difference in locking effect compared to a standard hex nut. Even so, it will serve to prevent the loosened nuts from falling off and being lost. Hexagonal nuts with excellent anti-loosening effects include “double-type anti-loosening nuts” and “hard lock nuts”, but these are two sets of male and female parts, and the manufacturing cost is not low.
"Hard Rock Industry Co., Ltd. Hard Lock Nut Leaflet", 10S / 08.10 “2000 Screw General Catalog”, Tokyo Tatsumi Cooperative Association, January 2000, 19th edition pp. 222, 223 "Screw story", Yamamoto Atsushi Japanese Standards Association pp. 84-86

In addition to the above, as a measure to prevent hex nuts from loosening, incline both sides of the contact surface where the double nuts face each other under the name of “suppression spring stop”, or use one of the double nuts as a standard hex nut. The opposite side is a hexagonal nut that is inclined on one side, a washer that is inclined on one side is sandwiched between the two nuts, and one or both axes of the double nuts are inclined at a slight angle with the axis of the bolt, And there is technology to prevent bolts from loosening.
Japanese Patent No. 67333

In addition, the bolt head bottom is inclined at an angle of 1 to 3 ° with respect to the axis perpendicular to the axis perpendicular to the axis perpendicular to the axis, and the axis pre-tension and axis pre-pressure are used. There is a technology to prevent the bolt from loosening by absorbing the gap between the screw and the female screw.
JP-A-10-131967

In the name of "female thread body", the bottom surface of a single hex nut is tilted to increase the frictional force with the contact surface with the member to be fastened, and at the same time, the hex nut is loosened by locking the bolt male thread and hex nut female thread. There is also technology to stop.
Data stored in microfilm of Japanese Utility Model Sho 56-029309

There is a technique similar to that disclosed in Japanese Patent Application Laid-Open No. 10-131967 of “Patent Document 2”, although the applicant is different, as a method of tilting the bottom of the head of the hexagon bolt with the name “fastening bolt” to prevent the hexagon bolt from loosening. .
Data stored in microfilm of Japanese Utility Model Sho 50-088754

Nylon film is fused to the vicinity of the male screw tip of the hexagon socket head cap screw, Nylon is embedded by drilling on one side of the side near the male screw tip, Nylon in a shallow vertical groove on one side of the side near the male screw tip By filling the gap between the male screw and female screw to maintain the axial force for a long time, the method of embedding the screw, the method of baking powder resin around the outer periphery of the male screw tip, or the method of applying liquid resin to the outer periphery of the male screw tip There is also a way to stop it.
Unbrako Engineering Guide SPS Ambraco Corporation 2006/3 / 5K p. 30

Apply a solution containing epoxy resin adhesive in microcapsules to a part of the outer circumference of the bolt center (screw pitch x 5), and tighten the screw to ooze out the epoxy resin adhesive and fix it to the thread. In the high adhesion type, there is a method of curing and locking to a practical strength after 20 to 30 hours, and in the quick-drying type, curing and locking to a practical strength after 1 to 2 hours, and simultaneously sealing.
THE HANDBOOK 2009 Standard Accessory Parts Nabeya Bi-Tech Co., Ltd. pp. 56,57

The invention of the same inventor as the present application and the applicant's application includes changing the head into a two-part hexagon socket head bolt and a threaded part and separating the truncated conical perforated bottom inclined cylindrical cap. Is a "non-parallel spacing" in which the bottom surface is inclined with respect to the plane perpendicular to the axis and the height of the top surface is extended vertically upward from the lowest end of the inclined bottom surface to be lower than the parallel surface with respect to the inclined bottom surface. 2 piece 1 piece wedge lock cap with a structure that fits by inserting a hexagon socket headed conical head male screw from the top side into a truncated conical perforated bottom and top non-parallel inclined cylindrical cap There are bolts.
Japanese Patent Application No. 2009-121676 (Japanese Patent No. 4385307)

  In the case of a bolt, even if it cannot be compared with the looseness of the nut, the "spring washer" can be rotated by hooking the claw of the "spring washer" cutting part on the bottom seating surface of the hexagon bolt head and the surface of the member to be fastened. In the method of preventing the spring, the elastic force of the “spring washer” is extremely small compared to the magnitude of the “pretension” in the axial direction of the bolt, and a locking prevention effect cannot be expected. This means that the toothed washer is very similar, meaning that there is no effective “loosening prevention” measure using a bolt alone.

  Also, if the embedded length of the bolt screw part exceeds about three times the bolt diameter, even if it can be expected that an effective fastening effect can be expected, the screw part may not be lengthened unnecessarily. There is a case where it is useless to lengthen the threaded portion in expectation for fastening by the pre-tension. On the contrary, the length of about 3 times can be said to be the “boundary length” of whether to loosen or not loosen.

  The wedge lock cap bolt with one set of two parts in which the bolt head and male thread part shown in the section “0010” are divided into two parts exhibits remarkable locking, but part of the conventional cold forging manufacturing process is In order to change, a new forging die and an investment in the production line incidental to it will be required. By using the bolt locking technology and the bolt locking technology without investing so much equipment, these nuts can be used by external forces such as vibration from the direction perpendicular to the axis while using standard nuts. An effective means for preventing the nuts from loosening is required.

  According to the present invention, in contrast to the slack caused by repeated impacts or vibrations in the direction perpendicular to the axis of such conventional bolts, the slack according to the well-known innocent axial direction using the “spring washer” or “toothed washer”. The purpose is not to prevent the bolts but to loosen the bolts and nuts fundamentally by means based on the elastic expansion of an elastic body that is inserted into the groove at the tip end of the bolt and bends.

  In order to achieve the above-mentioned object, the present invention provides about 0.173 to 0.00 of the “nominal number of screw” on the central axis of the male screw end of the hexagon socket head bolt, hexagon bolt, flanged hexagon bolt or square bolt. The diameter of the insertion hole dc equivalent to 315 times the diameter and the depth h corresponding to about 0.7 to 0.77 times the diameter of the groove, and the width of the groove fit into this "special E-shaped retaining ring 2" A “true-character groove T” having a width obtained by adding a numerical value of 0.1 to 0.5 mm corresponding to the “nominal diameter d” to the thickness t is machined to the same depth as the insertion hole dc. The "G-shaped groove T" is a "special E-shaped retaining ring 2" in which the shape of the "E-shaped retaining ring 2a" of the JIS standard and the manufacturer's standard is squared. The “mountain fold a” portion or “semicircle” that fits into the insertion hole dc at the center of the “groove T” ”Aa” part is provided, and is configured to be inserted and fitted along the insertion slot dc, and can withstand repeated “screwing / relaxation” with the elastic expansion force of “special E-shaped retaining ring 2”; The outer edge of the “special E-shaped retaining ring 2” is brought into close contact with the internal diameter di of the female screw to be screwed into the male screw by elastic expansion force, filling the gap between the female screws and maintaining a preload that is perpendicular to the axis. Hexagon socket head cap bolts, hexagon bolts, flanged hexagon bolts, or square bolts with a structure that locks the male screw through a “slot” at the end of the bolt male screw.

  The “special E-shaped retaining ring 2” shown in “Claim 2” uses “spring steel” or “stainless steel for spring” and is subjected to heat treatment such as quenching and tempering after punching and is elastic. Applying force, the maximum outer diameter on the tip side is the dimension obtained by adding 0.16 to 0.45 mm to the effective diameter de of the screw corresponding to “Nominal Thread” M8 to M30, and the E-shaped root folds In the direction of part a or “semi-circular bend aa”, the outer edge is screwed to the inner diameter di of the mating female screw while retaining the elastic force of bending at the time of fastening by forming a straight part with a taper angle of about 10 degrees. Form the shape in which three or four ridges of the pitch are in close contact, the thickness is set to a thickness t that can be stamped and formed, and the “mountain fold a” or “semicircle bend aa” part is inserted and fitted along the insertion hole dc. Hexagon socket head cap screw and hexagon bolt , It has been in flanged hex bolt or square bolt.

  Furthermore, in addition to the loosening prevention of the hexagon socket head bolt, hexagon bolt, flanged hexagon bolt or butterfly bolt itself with the "female screw member 10", the "planting bolt 3" in "Claim 3" and other " In “male thread”, instead of using “female thread member 10” to be screwed in, without using “spring washer”, JIS standard “hex nut 4”, “hexagon” It includes a method for preventing loosening of the cap nut 5 "or" bow nut 6 ".

  The E-EXT lock bolt of the present invention, that is, a locking bolt by elastic expansion of a retaining ring bent by fastening, is provided with a slit at the tip of the bolt screw portion, and is made of “special E” made of spring steel or spring stainless steel. Despite having a simple shape that incorporates the retaining ring 2 ", the" special E-shaped retaining ring 2 "with an outer diameter of 0.16 to 0.45mm added to the" effective thread diameter de "and the mating female screw at the time of fastening The preload in the direction perpendicular to the axis is maintained by the elastic expansion force of the deflection due to the size difference from the “inner diameter di”, and the maximum diameter outer edge works in the same way as the effect of filling the gap between the “female screw / female screw”. The bolt screw part is prevented from rotating through “slit” at the tip of the bolt screw part to prevent the bolt itself from loosening.

  Specific effects of the locking prevention of the present invention “E-EXT lock bolt” include the following nine items (A) to (I). First, (i) the effect of preventing loosening is exhibited regardless of the type of hexagon socket head cap screw, hexagon bolt, flanged hexagon bolt or square bolt.

(B) The loosening prevention effect does not depend on the axial pre-tension due to the screwing torque or the adhesive fixing of the epoxy adhesive and the method of fusing the nylon film to a part of the thread. 2 ”is an anti-loosening by elastic expansion force, and exhibits the anti-loosening effect without tightening the bolts.

(C) Withstands repeated screwing and loosening of bolts, and the anti-loosening effect does not deteriorate over time.

(D) Naturally, a spring washer is not required, and even if the flat washer 8 is used for the purpose of not damaging the surface of the fastened member 9, the effect of preventing loosening is exhibited.

(E) In addition to “locking prevention” on the implanted side of the implanted bolt 3, a standard hexagonal nut is screwed into the inner side of the “slot” side of the male screw as a “double lower nut 4 a” By replacing the stacked standard hexagon nut with the “upper nut”, the strength of the external thread is not reduced, and the “upper nut” exhibits a loosening prevention effect and prevents the “double lower nut 4a” from being loosened.

(F) In this stud bolt, the use of the cap nut 5 or butterfly nut 6 as well as the hexagonal nut 4 in the section “e” exhibits a loosening prevention effect.

(G) Except for the punching and forming equipment for “Special E-type retaining ring 2”, the investment amount of the manufacturing equipment can be small, and “Special E-type retaining ring 2” is not limited by the bolt length. It is sufficient to use one type per call.

(H) The stamping process of “special E-shaped retaining ring 2” has an industrial technical base for manufacturing “E-shaped retaining ring 2a” stipulated by the current JIS regulations. That's it.

(Li) Since the bolt strength can be covered with the number of pitch ridges found on the nut, it is necessary to provide a “complete thread” with a length equivalent to the outer diameter of the screw called “Nominal Thread” below the neck of the bolt. For example, a bolt tip “slot” having a length of “complete screw length + slot depth” does not affect the “tensile strength” of the bolt at all. As a specific example, when the slit depth of the bolt tip of M10 is 8 mm, the minimum length of the bolt of the present invention may be 18 mm or more, and a good cutting length can be applied to a bolt of M10 × 20 or more. .

  Assuming that the "screw outer diameter d" corresponding to the nominal size of the screw is the screw length of the entire screw bolt and the tensile strength ratio is 100%, the tensile strength ratio of the entire screw bolt corresponding to the "slot depth h" is It becomes 77.4-90.1% shown in FIG. 11, and the average value of 9 sizes of the nominal numbers M8-M30 of the screw is 85.8%. In the case of “total thread length L”, which is a length obtained by adding “slot depth h” to “screw outer diameter d”, the average tensile strength ratio 85.8% of “slot depth h” is “bonus” ", Which shows no influence on the" tensile strength "of the bolt.

  Hereinafter, embodiments of the “E-EXT lock bolt” of the present invention will be described with reference to FIGS. Since the dimensions of each part of the bolts specified by JIS are almost proportional to the nominal d, the required dimension ratios of the bolt tip and each part of the “special E-shaped retaining ring 2” are calculated based on the nominal M10. The elastic expansion force is adjusted and confirmed using the actual JIS-designated “E-type retaining ring 2a”. FIG. 1 shows a pre-assembly state and a post-assembly state of a slotted hexagon socket head cap screw, hexagon bolt and square bolt, and “special E-shaped retaining ring 2” according to the present invention.

When assembling with an automatic manufacturing device, use the “pushing jig” with an outer diameter that does not exceed the opening width of the “special E-shaped retaining ring 2”. Alternatively, the “semicircular bend aa” portion can be inserted along the insertion hole dc having a depth equivalent to the depth of the slit of “the width T of the straight groove”. The “mountain fold a” portion or the “semi-circular bend aa” portion serves to maintain the normal posture of the “special E-shaped retaining ring 2” when being softly fixed to the back of the insertion hole dc.

In addition, the “special E-shaped retaining ring 2” is flat because the tip crest width of the “inner diameter di” of the mating female screw is 1.25 times the crest width of the outer diameter portion of the male screw. In addition, there is no occurrence of “bending” that bites into the “inner diameter di” of the mating female screw that contacts this. However, the peak width of the inner diameter is 0.195 mm for size M8, 0.234 mm for M10, 0.273 for M12, 0.312 mm for M14 and M16, and it is safe for relatively small sizes of M8 and M10. Since the thickness of the razor blade is about twice the thickness of 0.1 mm, and the thread of the female thread is not generally as smooth and smooth as the mirror finish, it is recommended to use a lubricant when fastening Is done.

  FIG. 2 shows a side view of a state in which the “special E-shaped retaining ring 2” is incorporated in a hexagon socket head cap screw of nominal size M10, and FIG. 3 shows an example of a hexagon bolt of nominal size M10.

  FIG. 4 shows a comparison diagram between the “special E-shaped retaining ring 2” and the JIS-defined “E-shaped retaining ring 2a”. The prototype of the product of the present invention was tested using the “E-type retaining ring 2a” defined by JIS, but it was different from the intended use of the “E-shaped retaining ring 2a” and its outer shape was circular and elastic. The "inner diameter di" of the mating female screw due to expansion is a one-point contact, and a good anti-loosening effect cannot be obtained due to insufficient elastic expansion force. The result of using a prototype that was designed in the shape of Fig. 4 using an unmatched CAD after the test, and that was made by heat-treating the heat-treated "spring steel plate" that had been quenched and tempered with a micro-circular grindstone of a mini router. A loosening prevention effect was obtained.

  Fig. 5 shows that "slots" are machined on both the implantation side and nut side of the "planting bolt 3", the "special E-shaped retaining ring 2" is fitted, and the standard hexagonal nut 4 is made into a double nut. The embodiment using the washer 7, the embodiment of the double cap nut in which the “cap nut 5” is stacked on the “double lower nut 4 a”, and the embodiment of the “bow nut 6” are shown. In the case of “Cut Nut 6”, the pre-tensioning of the pre-pressure in the direction perpendicular to the axis due to the elastic expansion force of the “special E-shaped retaining ring 2” that is unrelated to the axial pre-tension, which reaches about 20 times the screwing torque, Locked by contact at multiple positions of the screw “inner diameter di” and the thread pitch crest “3-4 crests”, and can be attached and detached by hand, but it does not loosen at all by the right angle vibration. As long as we evaluate the results of the “prototype / experiment” process, we are very satisfied.

  By the way, regardless of the nominal size of the screw, both the “valley” of the bolt and the “mountain” of the inner diameter of the nut are not sharp triangular protrusions, but their apexes are slightly flat, and “special E-shaped retaining ring 2” Although there is no “biting” that cuts an object with a sharp blade edge when it is in close contact with the “inner diameter di” of the nut, applying a lubricant to expect a smooth “screwing” will not be contrary to expectations. “Screw”. However, despite the fact that the lubricating oil was applied, the oil film at the contact portion between the “special E-shaped retaining ring 2” that contributed to lubrication and the mating female thread “inner diameter di” was cut off after the fastening, and the “special E-shaped retaining ring” It becomes a locked state by elastic expansion without slipping of “2”, and loosening of both the male screw and the female screw is prevented. This fact can be said to be a “loosening prevention” effect worthy of special mention of the present invention.

  FIG. 6 shows the data of the “effective diameter de” and the “inner diameter di” of the female thread necessary for the design of the “special E-shaped retaining ring 2” corresponding to the nominal size of the screw. It is graphed as basic data for the design drawings shown in FIGS. A value of 0.16 to 0.45 mm as a “dimension to be added to the effective diameter” as a maximum outer diameter value of the “special E-shaped retaining ring 2”, which is different for each nominal diameter of the screw, is also investigated and listed.

  FIG. 7 shows the slits and bolts of “holding leg width W”, “plate thickness t”, “true-character groove width T” necessary for the drawing of “special E-shaped retaining ring 2” corresponding to the designation of the screw. An “insertion hole dc” equivalent to the depth of the “slot” at the tip is shown in contrast to the drawing.

  In FIG. 8, since the nominal size of the screw is almost proportional, the required dimensions are calculated using the nominal value M10 as a model as a reference value, and plotted in a standard diagram with a scale of 4: 1.

  9 picks up and draws six sizes of screw nominals M8, M10, M12, M14, M16 and M20, and FIG. 10 picks up and plots three sizes of screw nominals M22, M24 and M30. . Other “nominal” items are omitted because they are almost proportional. FIG. 10 is a chart of the total thread length L with a tensile strength rate of 100% and the tensile strength rate (%) of the part with a depth of h.

  In addition, the plate thickness t of the “special E-type retaining ring 2” for each nominal thread size is in accordance with the “plate thickness t” example of “sheet thickness t” that can be stamped and formed with the manufacturing results of the “E-type retaining ring 2a” of JIS. Since the E-shaped root portion is provided with a mountain fold a or a radial bend aa that fits into the “insertion hole dc”, it can be pushed in along the “insertion hole dc” and softly fixed. . Further, this mountain fold a or radius bend aa serves to maintain a normal posture in the set state of the “special E-shaped retaining ring 2”.

Structure of assembled locking bolt with elastic retaining ring of the present invention and sketch of assembly state The side view of the Example in the hexagon socket head bolt of this invention Side view of the embodiment of the hexagon bolt of the present invention Comparison of special E-type retaining ring of the present invention and JIS standard E-type retaining ring Outline drawing of examples of loosening prevention of nuts, hex nuts and cap nuts fastened to studs Nominal number of screw to be added to the effective diameter / internal diameter and effective diameter of the screw that is the basis of the outer diameter of the special E-shaped retaining ring Dimensional drawing of special E-type retaining ring and bolt end Detailed dimensional drawing of special E-shaped retaining ring and mating female thread inner diameter based on nominal M10 Dimensional drawing of special E type retaining ring for nominal M8 ~ M20 Dimensional drawing of special E type retaining ring for nominal M22 to M30 Chart of total thread length (L) with a tensile strength factor of 100% and tensile strength factor (%) at the parting depth h

1 Male thread 2 Special E-type retaining ring 2a JIS-designated E-type retaining ring 3 Stud bolt 4 Hexagon nut 4a Double lower nut 5 Cap nut 6 Bow nut
7 Female thread 8 Plain washer 9 Fastened member
10 Female thread member
B Internal tooth width of internal thread
L Length of all bolts
T Width of straight groove W Width of back of special E-shaped retaining ring
a Mountain fold aa Radial bend b Female thread root tooth width d Thread nominal diameter and male thread outer diameter da Male thread root diameter de Effective thread diameter di Female thread inner diameter h ”Depth t Special E-type retaining ring plate thickness

Claims (3)

  An insertion hole (dc) having a diameter equivalent to about 0.173 to 0.315 times the "nominal diameter of the screw" on the center axis of the end of the male threaded portion of the hexagon socket head bolt, hexagon head bolt, flange head hexagon bolt or square bolt Perforated at a depth (h) corresponding to a dimension equivalent to about 0.7 to 0.77 times, and the width of the groove is set to the thickness (t) of the “special E-shaped retaining ring (2)” that fits into the “screw” A “true groove (T)” with a width of 0.1 to 0.5 mm corresponding to “Nominal (d)” is processed to the same depth as the insertion hole (dc). The "E-shaped retaining ring (2)" in the shape of the "E-shaped retaining ring (2a)" of the JIS standard and the manufacturer's standard is used as the "E-shaped retaining ring (2)". “Mountain fold (a)” that fits into the insertion hole (dc) in the center of the “groove (T)” of the single letter on the side of the root Alternatively, a “semi-circular bend (aa)” portion is provided, and a structure that is slid along the insertion opening (dc) to be inserted and fitted, and is “screwed in” by the elastic expansion force of the “special E-shaped retaining ring (2)”.・ It can withstand repeated “relaxation” and the outer edge of “special E-shaped retaining ring (2)” is brought into close contact with the inner diameter (di) of the female screw to be fastened with the external expansion force. Hexagon socket head cap screw, hexagon bolt, flanged hexagon bolt or square bolt with a structure that locks the male screw via a "slit" at the tip of the bolt male screw. The “special E-shaped retaining ring (2)” in “Claim 1” uses “spring steel” or “stainless steel for spring”, and is subjected to heat treatment of quenching and tempering after punching and forming an elastic force. The maximum outer diameter at the tip side is the dimension obtained by adding 0.16 to 0.45 mm to the effective diameter (de) of the screw corresponding to “Nominal Thread” M8 to M30. By forming a straight portion with a taper angle of about 10 degrees toward the direction of the fold (a) or “semicircular bend (aa)”, the outer edge is a female screw while retaining the elastic force of bending at the time of fastening. 3 to 4 threads of the screw pitch are in close contact with the inner diameter (di) of the steel sheet, and the thickness is set to a thickness (t) that can be stamped and formed, and the “mountain fold (a)” portion or “semi-circular bending (aa)” ”Part is inserted and fitted along the insertion hole (dc) and softly fixed. Hexagon socket head bolts of 1 ", hexagonal bolt, flanged hexagonal bolts or square volts.   In addition to preventing loosening of the hexagon socket head bolt, hexagon bolt, flanged hexagon bolt or square bolt itself with the "female thread member (10)" in "Claim 1", the implanted bolt (3) and other " On the nut side of the male thread, instead of using a “female thread member (10)” to be screwed in, a “JIS standard hexagonal nut (fastened to the male thread” without using a “spring washer” ( 4) A method for preventing loosening of the hexagonal cap nut (5) or the wing nut (6).