Abstract:
The present invention is a lock nut which fastens to enable a downstream bent portion of a spiral coil spring to be a stopper point so that the diameter of the spiral coil spring is extended overall, and which unfastens to release the downstream bent portion from the stopper point and enable an upstream bent portion of the spiral coil spring to be a stopper point so that the diameter of the spiral coil spring is extended overall, thus enabling the lock nut to be easily fasten without sacrificing elastic fastening forces of the conventional lock nut, preventing the lock nut from easily unfastening by unintentional external force, and enabling the lock nut to unfasten only by intentional external force. The above described operation can be performed without increasing manufacturing cost, and the lock nut can be manufactured to be disposable in order to achieve preventing accidents in advance.

Description:
TECHNICAL FIELD 
     The present invention relates to a lock nut, and more particularly to a lock nut capable of being fastened under anti-release condition with high reliability and being released by the intended external force. 
     BACKGROUND ART 
     Usually, in order to prevent the lock nut from being released, a washer or a coil spring is inserted between the bolt and the nut. Conventional lock nut having a spiral coil spring between the bolt and the nut is disclosed in Korean patent No. 10-701782 and 10-701643. This lock nut includes a thread part on the inner surface of the upstream side of the fastening direction which is engaged with the bolt, and a non-thread part having a larger inner diameter than that of the thread part on the downstream side of the fastening direction and a spiral coil spring being touched on the inner wall of the non-thread part with an interval. In the non-thread part of the lock nut are formed an upstream step and a downstream step having a reduced diameter respectively to prevent the spiral coil spring in the non-thread part from leaving out. 
     On the surface of the downstream step of the lock nut facing the axial line of the bolt is formed a recess, in which the downstream bent portion extending outward at the downstream end of the coil spring is inserted and fixed, and the upstream end of the spiral coil spring is touched internally on the non-thread part, and is separated along the axial direction at the upstream step. And the spiral coil spring has the inner surface being clamped with the thread part of the bolt. 
     The above bolt is operated as follows. If a user inserts the bolt into the lock nut and turns it to the fastening direction, firstly the thread part of the bolt is engaged with the thread part of the nut, then the thread part of the bolt and the spiral coil spring is engaged to each other. Accordingly, the spiral coil spring is twisted forward fastening direction, and as the downstream bent portion is fixed in the recess, the spiral coil spring will be enlarged radially, then the front end of the thread part of the bolt would smoothly pass through the spiral coil spring. If the turning of bolt toward the fastening direction is stopped, the enlarged spiral coil spring is reduced radially to be fastened with the thread part of the bolt elastically. In this state, the spiral coil spring keeps fastening the thread part of the bolt elastically, so that the lock nut would not be released from the bolt by any unwanted external force. 
     But in case that the bolt is turned toward the release or unlocking direction for maintenance, as the downstream bent portion of the spiral coil spring is fixed in the recess, the spiral coil spring will be reduced radially, so the turning action of the nut toward the release direction becomes difficult. If the user turns the lock nut toward the release direction with high strength, the spiral coil spring would be broken down at the downstream bent portion, and the spiral coil spring without the downstream bent portion would remain in the non-thread part in spite of the turning action with high strength. As a result, the lock nut could not be released without damaging the lock nut itself. 
     In order to overcome the above problem, a solution may be proposed that an upstream bent portion extending radially outward is formed at the upstream end of the spiral coil spring similarly as that of the downstream end, and a slot extending radially is formed on the non-thread part facing the upstream bent portion. If the lock nut is turned toward the fastening direction as the upstream bent portion being in the slot, as the downstream bent portion of the spiral coil spring is fixed in the recess, the overall spiral coil spring would be radially reduced, and the upstream bent portion becomes deformed in the release direction along the inner surface of the non-thread part, then it will be engaged into the slot, so that the overall spiral coil spring will be radially extended. But this proposal has a problem that when the upstream bent portion is deformed along the inner surface of the non-thread part and is engaged into the slot, both ends of the spiral coil spring are fixed in the upstream bent portion and the downstream bent portion, so that, even though the upstream bent portion may be radially extended, the downstream bent portion still remains radially reduced, and it is yet difficult to release the lock nut from the bolt. 
     To solve this problem, another solution may be proposed that the diameter of the spiral coil spring may be enlarged only on the upstream end than the other part, so that when the lock nut is turned toward the release direction, only the upstream end of the spiral coil spring is reduced radially to prevent the thread part of the bolt from being fastened. But this solution also has a problem that, as the diameter of the upstream end of the spiral coil spring is larger than that of the other part, the other part of the spiral coil spring is separated more inwardly from the non-thread part than that of the conventional one, the size of the lock nut would be inevitably larger, which will result in the increased material cost and manufacturing cost. If the thickness of the spiral coil spring is reduced to cope with this problem, then the fastening force of the spiral coil spring against the thread part of the bolt would be reduced, so the reliable anti-release function would not be achieved. 
     And, if it is repeated that the spiral coil spring is enlarged and then reduced radially when the lock nut is fastened, and the spiral coil spring is enlarged and then reduced radially when the lock nut is released, the safety accident may happen when the lock nut is applied on the fastening device of the bridge, railroad, and so on. 
     DISCLOSURE 
     Technical Problem 
     The present invention is proposed to solve the above mentioned problems. 
     Technical Solution 
     According to an aspect of the present invention, there is provided a lock nut in which, when the lock nut is to be fastened, the downstream bent portion of a spiral coil spring becomes engagement point so that the overall spiral coil spring is radially enlarged, and when the lock nut is to be released, the engagement of the downstream bent portion is released and the upstream bent portion becomes engagement point so that the overall spiral coil spring is radially enlarged. 
     According to another aspect of the present invention, there is provided a lock nut in which, both ends of the spiral coil spring are positioned in the non-thread part of the lock nut in the radially enlarged state by a fixing means, and the fixing means is manually released by the user and the spiral coil spring is radially reduced and contacts the thread part of the bolt, and one end of the coil spring is fixed by the other fixing means to keep the coil spring in the radially enlarged state. 
     Advantageous Effects 
     According to the first aspect of the present invention, the elastic fastening force is not reduced and the fastening action of the nut is easy, and unwanted release by the unintended external force will not happen, and these advantages could be attained without increasing the cost, and as the lock nut is made to be disposable, the safety accident associated with the reuse of the lock nut could be prevented. 
     According to the second aspect of the present invention, in case that the positioning of the fastening object is not proper, or the order of fastening the bolt and nut is not correct, or foreign material is induced into the fastening object, so it is required to release the bolt and lock nut, it is possible to release the lock nut to save the resource. And the user can fasten the bolt and lock nut with only one hand, so the assembling work in the high place is easy and safe. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The above and other objects and advantages of the invention will become more apparent by describing a preferred embodiment with reference to the accompanying drawings in which: 
         FIG. 1  is a concept view of the spiral coil spring in fastening state according to the first embodiment of the invention. 
         FIG. 2  is a concept view of the spiral coil spring of  FIG. 1  in released state 
         FIG. 3  is a view of the nut of the first embodiment in which the spiral coil spring is not inserted 
         FIG. 4  is a view of the nut of the first embodiment in which the spiral coil spring is inserted 
         FIG. 5  is a view of the nut of the second embodiment in which the spiral coil spring is not inserted 
         FIG. 6  is a view of the nut of the second embodiment in which the spiral coil spring is inserted 
         FIG. 7  is a perspective of the nut of the second embodiment in which the spiral coil spring is radially enlarged 
         FIG. 8  is a perspective of the nut of the second embodiment in which the spiral coil spring is radially reduced 
         FIG. 9  is a perspective of the nut of the modified embodiment in which the spiral coil spring is radially enlarged 
         FIG. 10  is a perspective of the nut of the modified embodiment in which the spiral coil spring is radially reduced 
         FIG. 11  is section illustrating an arch and cams are formed on the step of the downstream end of the nut of  FIG. 5   
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Best Mode 
     According to the first embodiment of the invention, there is provided a lock nut into which a bolt is engaged from an upstream end to a downstream end and in which a spiral coil spring is inserted in the nut, and on the downstream end of the spiral coil spring is formed a downstream bent portion which is bent radially outward, and the upstream end of the spiral coil spring is positioned to face the downstream bent portion radially, and the spiral coil spring is coiled so that a bolt should penetrate from the upstream end to the downstream end and could be fastened with the spiral coil spring, and the nut has a thread part on the inner surface of the upstream to be engaged with the bolt, and the nut has a non-thread part on the inner surface of the downstream, the non-thread part has an inner diameter larger than that of the thread part and houses the spiral coil spring with a gap, and the non-thread part includes an upstream step and a downstream step with the reduced diameter, and on the surface of downstream step exposed on the axial direction of the bolt is formed a recess, into which the downstream bent portion of the spiral coil spring is inserted, so that, if the external force is applied at the spiral coil spring in the release direction of the nut, the downstream bent portion should leave out from the recess by being pulled radially inward, and the upstream end of the spiral coil spring contacts against the upstream step, and a stopper extending inward radially is formed on the inner surface of the non-thread part adjacent to the upstream step, and the stopper is positioned to be separated from the upstream end of the spiral coil spring toward the release direction of the bolt. 
     According to the second embodiment of the invention, there is provided a lock nut into which a bolt is engaged from an upstream end to a downstream end and in which a spiral coil spring is inserted in the nut, and on the downstream end of the spiral coil spring is formed a downstream bent portion which is bent radially outward, and the upstream end of the spiral coil spring is positioned to face the downstream bent portion radially, and the spiral coil spring is coiled so that a bolt should penetrate from the upstream end to the downstream end and could be fastened with the spiral coil spring, and the nut has a thread part on the inner surface of the upstream to be engaged with the bolt, and the nut has a non-thread part on the inner surface of the downstream, the non-thread part has an inner diameter larger than that of the thread part and houses the spiral coil spring with a gap, and the non-thread part includes an upstream step and a downstream step with the reduced diameter, and on the surface of downstream step exposed on the axial direction of the bolt are formed a recess and another recess, into which the downstream bent portion of the spiral coil spring is selectively and detachably inserted, and the upstream end of the spiral coil spring elastically contacts against the upstream step, and a stopper contacting against the upstream end elastically is formed on the upstream step or the non-thread part adjacent to the upstream step, and the other recess is positioned to be separated from the one recess in the downstream of the fastening direction. 
     Hereinafter, the first embodiment of the invention will be described based on  FIG. 1  to  FIG. 4 . A lock nut  100  according to the invention can be engaged with a bolt  50  from an upstream end to a downstream end and includes spiral coil spring  10  as shown in  FIG. 4 . On the downstream end of the spiral coil spring  10  is formed a downstream bent portion  11  which is bent outward as shown in  FIG. 1 . The upstream end  12  of the spiral coil spring  10  is formed on the diametrically opposite of the downstream bent portion  11 . The spiral coil spring  10  is coiled so that the thread part  51  of the bolt  50  can penetrate from the upstream end  12  to the downstream end and is fastened with the spiral coil spring  10 . 
     As shown in  FIG. 4 , in the state that the downstream bent portion  11  of the spiral coil spring  10  is fixedly inserted into the recess  21  of the nut  20 , if a user makes the bolt  50  contact the upstream end of the spiral coil spring  10  and turns it in the fastening direction (clockwise in  FIG. 1 ), the spiral coil spring  10  contacts the thread part of the bolt  50  frictionally and is enlarged radially and allows the bolt  50  to easily enter into the downstream end of the spiral coil spring  10 . 
     As shown in  FIG. 2 , in the state that the downstream bent portion  11  of the spring  10  is fixed inserted into the recess  21  formed on the nut  20  and the bolt  50  penetrates the spring  10 , if the user turns the bolt in the releasing direction (counterclockwise in  FIG. 2 ), the spiral coil spring  10  will frictionally contact the thread part of the bolt  50  and become reduced radially, then it will prevent the bolt  50  from leaving out from the upstream of the spiral coil spring  10 . 
     As shown in  FIG. 3 , the nut  20  includes a thread part  22  on the inner surface of the upstream of the fastening direction with the bolt  50 , and a non-thread part  23  having a diameter larger than that of the thread part  22  and housing the spiral coil spring  10  with a gap on the downstream of the fastening direction. 
     The non-thread part  23  of the nut  20  includes an upstream step  23   a  and a downstream step  23   b  with the reduced diameter to prevent the spiral coil spring  10  in the non-thread part  23  from leaving out of the nut  20 . On the surface of the downstream step  23   b  of the nut  20  is formed a radially opened recess  21 . As shown in  FIG. 4 , the downstream bent portion  11  of the spiral coil spring  10  is engaged in the recess  21 , and the upstream end  12  of the spiral coil spring  10  contacts on the upstream step  23   a  elastically. 
     As the downstream bent portion  11  of the spring  10  is engaged in the recess  21 , if an external force in the release direction of the nut is applied on the spiral coil spring  10 , the downstream bent portion  11  can leave out of the recess  21  by being pulled radially inward. 
     As shown in  FIG. 3 , a stopper  24  projecting radially inward is formed on the inner surface of the non-thread part  23  adjacent to the upstream step  23   a . This stopper  24  is positioned to be separated with some interval from the upstream end  12  of the spiral coil spring  10  in the release direction of the bolt  50 . This stopper  24  can be made by punching from outside so that one end of the stopper  24  is attached to the nut  20  and the other end of the stopper  24  projects inward. 
     Among the walls forming the recess  21 , the edge  21   a  of the wall facing the inner bent portion of the downstream bent portion  11  can be formed to have acute angle so that, if an external force having a certain strength is applied, the downstream bent portion may be cut and divided from the spiral coil spring  10 . 
     The above mentioned lock nut will function as follows. If the user inserts the thread part  51  of the bolt  50  into the thread part  22  of the lock nut  100  and turns it in the fastening direction, the thread part  51  of the bolt  50  will penetrate the thread part  22  and be fastened with the thread part  22  of the nut  20 , and if the user further turns the bolt  50  in the fastening direction, the thread part  51  of the bolt  50  will frictionally contact against the upstream end  12  of the spiral coil spring  10  and press the spring  10  in the fastening direction. Then, as the downstream bent portion  11  of the spring  20  is fixedly engaged in the recess  21  of the nut  20 , the spiral coil spring  10  will be enlarged radially, so the thread part  51  of the bolt will pass through the spiral coil spring  10  easily. If the user stops the turning of the bolt  50  in the fastening direction, the pressing force by the thread part  51  of the bolt  50  to the spiral coil spring  10  is released, and the spring  10  becomes reduced radially and seats in the groove of the thread part  51  of the bolt  50 , then it will elastically press the thread part  51  of the bolt  50  radially inward. As a result, the clamping between the nut  20  and the bolt  50  would not be released by unintended external force. 
     In this state, if it is necessary to release the nut  20  from the bolt  50  for maintenance, the user should turn the nut  20  in the release direction, then the thread part  51  of the bolt  50  will frictionally contact against the spiral coil spring  10  and press the spring  10  in the release direction and make the spring  10  become radially reduced. Then if an external force with a certain strength or more in the release direction is applied on the downstream bent portion  11  of the spiral coil spring  10 , the downstream bent portion  11  may leave out of the recess  21  by being pulled radially inward, or the inner bent portion of the downstream bent portion  11  is pressed intensively at the edge  21   a  of the recess  21  and cut from the spring  10 . As a result, the upstream end  12  and the downstream bent portion  11  of the spring  10  become free ends in the fastening or release direction and become movable along the non-thread part  23  against the nut  20 . In this state, if the user turns the nut  20  further in the release direction, the upstream end  12  of the spring  10  contacts the stopper  23 , and the stopper  24  will press the upstream end  12  of the spring  10 , so the spring  10  becomes enlarged radially, then the bolt  50  will be smoothly turned in the release direction without any restriction from the spiral coil spring  10 . 
     The spiral coil spring  10  is disposal and could not be used again, because the downstream bent portion  11  of the spring  10  engaged in the recess  21  may be deformed or cut away if the spring  10  is to leave out of the recess  21 . As a result, according to the present invention, reuse of the deformed or damaged spiral coil spring  10  is basically impossible. Therefore, the safety accident caused by the reuse of the deformed or damaged spiral coil spring  10  could be effectively prevented. 
     Though the stopper  24  according to the above embodiment is described to project radially inward from the inner surface of the non-thread part  23 , as a modified embodiment, the stopper  24   a  may project from the upstream step  23   a  toward the downstream step  23   b  to achieve the same technical effect. 
     The second embodiment of the invention will be described based on  FIG. 5  to  FIG. 8 . The lock nut  100  includes a spiral coil spring  10  the same with that of the first embodiment. 
     As shown in  FIG. 7 , in the state that the downstream bent portion  11  of the spiral coil spring  10  is inserted into the recess  21  of the nut  20 , if a user makes the bolt  50  contact the upstream end of the spiral coil spring  10  and turns it in the fastening direction (clockwise in  FIG. 1 ), the spiral coil spring  10  contacts the thread part of the bolt  50  frictionally and is enlarged radially, so allows the bolt  50  to easily enter into the downstream end of the spiral coil spring  10 . 
     In the state that the downstream bent portion  11  of the spring  10  is inserted into the recess  21  formed on the nut  20  and the bolt  50  penetrates the spring  10  as shown in  FIG. 2 , if the user turns the bolt in the release direction (counterclockwise in  FIG. 2 ), the spiral coil spring  10  will frictionally contact the thread part  51  of the bolt  50  and become reduced radially, then it will prevent the bolt  50  from leaving out from the upstream of the spiral coil spring  10 . 
     As shown in  FIG. 5 , the nut  20  includes a thread part  22  on the inner surface of the upstream of the fastening direction with the bolt  50 , and a non-thread part  23  having a diameter larger than that of the thread part  22  and housing the spiral coil spring  10  with a gap on the downstream of the fastening direction. 
     The non-thread part  23  of the nut  20  includes an upstream step  23   a  and a downstream step  23   b  with the reduced diameter to prevent the spiral coil spring  10  in the non-thread part  23  from leaving out of the nut  20 . As shown in  FIG. 7 , on the surface of the downstream step  23   b  of the nut  20  are formed a recess  21  and another recess  21 ′. As shown in  FIG. 7  and  FIG. 8 , the downstream bent portion  11  of the spiral coil spring  10  is selectively and detachably engaged in the recess  21  or the other recess  21 ′, and the upstream end  12  of the spiral coil spring  10  contacts on the upstream step  23   a  elastically and also contacts on the stopper S formed on the non-thread part  23  elastically. The stopper S is a projection which projects from the upstream step  23   a  toward the downstream step  23   b  or it may project from the inner surface of the non-thread part  23  radially inward. 
     If the downstream bent portion  11  of the spiral coil spring  10  is fixed in the recess  21 , and the upstream end  12  of the spiral coil spring  10  is pressed against the stopper S elastically, then the spiral coil spring  10  will be kept in radially enlarged state. Meanwhile, if the downstream bent portion  11  of the spiral coil spring  10  is fixed in the other recess  21 ′ and the upstream end  12  of the spiral coil spring  10  is pressed against the stopper S elastically, then the spiral coil spring  10  will be kept in radially reduced state. It is based on the principle that if the upstream end of the spiral coil spring  10  is pressed clockwise (in the fastening direction) and the downstream end is pressed counterclockwise (in the release direction), then the spring  10  becomes enlarged radially, and if the upstream end of the spiral coil spring  10  is pressed counterclockwise (in the release direction) and the downstream end is pressed clockwise (in the fastening direction), then the spring  10  becomes reduced radially. 
     Accordingly, the recess  21  is formed on a certain point of the downstream step  23   a  in which the downstream end of the spiral coil spring  10  is located when the spring  10  is enlarged radially as the upstream end  12  of the spring  10  is fixed by the stopper S. Meanwhile, the other recess  21 ′ is formed on a certain point of the downstream step  23   b  in which the downstream end of the spiral coil spring  10  is located when the spring  10  is reduced radially (contacting against the thread part  51  of the bolt  50 , that is, the spring  10  being free without any external force) as the upstream end  12  of the spring  10  is fixed by the stopper S. That is, the other recess  21 ′ is located in the downstream of the fastening direction against the recess  21  with some interval. 
     The above lock nut  100  will function as follows. 
     First, the spiral coil spring  10  should be positioned in the first mode (refer to  FIG. 7  in which the spiral coil spring  10  is enlarged radially) in which the upstream end  12  of the spring  10  contacts the stopper S and the downstream bent portion  11  is engaged in the recess  21 . 
     Next, the user inserts the thread part  51  of the bolt  50  into the thread part  22  of the nut  20  and turns the bolt  50  in the fastening direction, then thread part  51  of the bolt  50  passes through the thread part  22  of the nut  20  and becomes engaged with the thread part  22 . If the bolt  50  is further turned in the fastening direction, the thread part  51  of the bolt will easily penetrate into the spiral coil spring  10  without any restriction by the enlarged spring  10  entrapped between the stopper S and the recess  21 , and the clamping action of the lock nut  100  against the bolt  50  is completed. 
     In this state, if the positioning of the fastening object is not proper, or the order of fastening the bolt and nut is not correct, or foreign material is induced into the fastening object, so it is required to release the bolt and lock nut, the bolt  50  could be turned in the release direction as the ordinary bolt and nut to release the clamping between the bolt  50  and the lock nut  100 . 
     Then bolt  50  and the lock nut  100  is fastened again, and if there is no problem in the clamping or fastening state, then the user takes out the downstream bent portion  11  of the spiral coil spring  10  from the recess  21 , then as the overall spiral coil spring  10  is reduced radially, the downstream bent portion  11  is moved to the downstream of the fastening direction and positioned on the other recess  21 ′. Then the user inserts the moved downstream bent portion  11  into the other recess  21 ′ to achieve the second mode (refer to  FIG. 6  in which the spiral coil spring is reduced radially). 
     In the second mode, the spiral coil spring  10  is seated in the groove of the thread part  51  of the bolt  50  and elastically presses the thread part  51  of the bolt  50  radially inward, and the clamping between the lock nut  100  and the bolt is prevented from releasing by any unintended external force. In this state, if it is necessary to release the bolt and nut for maintenance, the user may set the spring  10  in the first mode, then the lock nut  100  can be released from the bolt  50  without any damage of the bolt and nut. 
     As mentioned above, in case that the positioning of the fastening object is not proper, or the order of fastening the bolt and nut is not correct, or foreign material is induced into the fastening object, so it is required to release the bolt and lock nut, it is possible to release the lock nut to save the resource. And the user can fasten the bolt and lock nut with only one hand, so the fastening work in the high place is easy and safe. 
       FIG. 11  shows an example modified from the second embodiment, in which an arch  52  having the slowly curved recess facing the head of the bolt  50  is formed on the downstream step  23   b  between the recess  21  and the other recess  21 ′. And, a pair of cams  60  are formed on the adjacent part between the recess  21  and the arch  52  and on the adjacent part between the other recess  21 ′ and the arch  52  respectively. These cams  60  help the downstream bent portion  11  of the spiral coil spring  10  leave out from the recess  21  or the other recess  21 ′ to be positioned on the arch  52  when a certain amount of force is applied in the fastening or release direction. Therefore, it is possible for the user to move the downstream bent portion  11  from one recess  21  to the other recess  21 ′ or reversely, that is, make the spiral coil spring  10  enlarged or reduced radially only by use of the fastening and releasing tool and without use of the user&#39;s hand or awl. 
       FIG. 9  shows another embodiment modified from the second embodiment, in which the other recess  21 ′ among the recess  21  and the other recess  21 ′ is removed. Instead, an elongated slot  30  is formed in the spiral direction on non-thread part  23  and adjacent to the stopper S, and the upstream end  12  of the spiral coil spring  10  is bent outward to form an upstream bent portion  12 ′ similarly to the downstream bent portion  11  of the spiral coil spring  10 , and the upstream bent portion  12 ′ penetrates into the slot  30 . 
     And, a stopper S′ projecting toward the axial line is formed on the upper wall  31  or the lower wall  32  of the slot  30  in the axial direction, but the stopper S′ is separated from the side wall  33  of the slot  30  positioned in the clockwise direction toward the counterclockwise direction, and the separated distance is set such that the spring  10  is enlarged radially when the upstream bent portion  12 ′ is engaged in the stopper S′, and the spring  10  is reduced radially when the upstream bent portion  12 ′ rides over the stopper S′ and positions between the side wall  33  and the stopper S′. 
     According to the above mentioned embodiment modified from the second embodiment, the user can manually select between the first mode (the spring is enlarged radially) as shown in  FIG. 9  and the second mode (the spring is reduced radially) as shown in  FIG. 10 . The function of this embodiment is similar to the above mentioned second embodiment and will be described as follows. 
     First, the spiral coil spring  10  should be positioned in the first mode (refer to  FIG. 7  in which the spiral coil spring is enlarged radially) in which the upstream bent portion  12 ′ of the spring  10  contacts the stopper S′ and the downstream bent portion  11  is engaged in the recess  21 . 
     Next, the user inserts the thread part  51  of the bolt  50  into the thread part  22  of the nut  20  and turns the bolt  50  in the fastening direction, then the thread part  51  of the bolt  50  passes through the thread part  22  of the nut  20  and becomes engaged with the thread part  22 . If the bolt  50  is further turned in the fastening direction, the thread part  51  of the bolt will easily penetrate into the spiral coil spring  10  without any restriction by the enlarged spring  10  entrapped between the stop S′ and the recess  21 , and the clamping action of the lock nut  100  against the bolt  50  is completed. 
     In this state, if the positioning of the fastening object is not proper, or the order of fastening the bolt and nut is not correct, or foreign material is induced into the fastening object, so it is required to release the bolt and lock nut, the bolt  50  could be turned in the release direction as the ordinary bolt and nut to release the clamping between the bolt  50  and the lock nut  100 . 
     Then bolt  50  and the lock nut  100  is fastened again, and if there is no problem in the clamping or fastening state, then the user takes the upstream bent portion  12 ′ of the spiral coil spring  10  out of the stopper S′ and position it between the side wall  33  and the stopper S′, then the overall spiral coil spring  10  is reduced radially and the second mode is achieved. 
     In the second mode, the spiral coil spring  10  is seated in the groove of the thread part  51  of the bolt  50  and elastically presses the thread part  51  of the bolt  50  radially inward, and the clamping between the lock nut  100  and the bolt is prevented from releasing by any unintended external force. In this state, if it is necessary to release the bolt and nut for maintenance, the user may hold the bent portion  12 ′ and press it toward fastening direction to be engaged in the S′ and set the spring  10  in the first mode, then the lock nut  100  can be released from the bolt  50  without any damage of the bolt and nut. 
     INDUSTRIAL AVAILABILITY 
     The embodiments according to the present invention can be used in the fields of bridges, railroad, atomic power plants or power distribution board in which the mechanical safety is very important.