GB2120345A

GB2120345A - Anti-loosening bolt

Info

Publication number: GB2120345A
Application number: GB08213806A
Authority: GB
Inventors: Zengoro Kikuta
Original assignee: Kurakichi Mochizuki
Current assignee: Kurakichi Mochizuki
Priority date: 1982-05-11
Filing date: 1982-05-12
Publication date: 1983-11-30
Also published as: FR2526891A1

Abstract

An anti-loosening bolt has a thread formation comprising two threads of opposite hand, in which a plurality of first ridges (14') is arranged at regular intervals, each of which ridges (14') extending outward at right angles to the axis of the shank (13) from about a half of the circumference of a cross section thereof, each of the ridges (14') being substantially crescent-shaped with both its end portions sinking gradually into the surface of the shank; and a similar plurality of second ridges (15') extend from substantially the remaining half of the circumference of the cross section of the shank, the second series (15) being so formed as to be staggered by 1/2 of their pitch from the first threads (14). This construction allows two nuts of opposite hand to both be threaded on the same shank, and they will thus be in a locked state. The thread can be formed by passing a threading tool along the shank in both directions successively while the shank is rotated in the same sense. <IMAGE>

Description

SPECIFICATION Anti-loosening bolt This invention relates to an anti-loosening boit, and more particularly to an anti-loosening bolt using two nuts.

In a conventional anti-loosening bolt using two nuts, the nuts are merely screwed on a thread of the bolt, and, therefore, a sufficient anti-loosening effect cannot be expected.

Figure 1 of the accompanying drawings shows a front elevation of one type of conventional antiloosening bolt 1 which co-operates with two nuts, 4, 5 illustrated in section in Figure 2. In this antiloosening bolt 1 a smaller-diameter screw 3 having a ieft-handed thread is provided at the front end of a screw 2 having a right-handed thread, and nut 4 and smaller-diameter nut 5, which are shown in Figure 2, are set on the screws 2, 3, respectively. When this anti-loosening bolt is used in practice, nut 4 is first set on the screw 2, and then the small-diameter nuts is set on the smaller-diameter screw 3 and tightened against nut 4.

Therefore, even if nut 5 superposed on nut 4 is turned so as to loosen nut 4, nut 5 receives the rotary force in the tightening direction because nut 5 is threaded in the direction opposite to the direction nut 4 is threaded in. As a result, the nuts 4, 5 are pressed against each other to prevent them from being loosened.

However, it is necessary in this bolt 1 to form two screws of different diameters on it. This complicates the constructions of the bolt 1, and increases its manufacturing cost. When nut 4 is set on the screw 2 it is liable to catch the stepped portion of the bolt making it difficult to set the nut 4 on the screw 2. Accordingly, it takes much time to tighten this bolt 1 due to the use of two nuts of different diameters.

An object of the present invention is to provide a novel anti-loosening bolt which has threads on a single non-stepped shank having a constant outer diameter, which permits the shank and threads to be formed simply, and the nut-tightening operation to be carried out easily.

Another object of the present invention is to provide a novel anti-loosening bolt having threads which permit both a nut having a right-hand thread and a nut having a left-hand thread to be screwed thereon.

According to the present invention there is provided an anti-loosening bolt comprising a plurality of first threads having ridges arranged at regular intervals, each of which ridges extends outward at right angles to the axis of the shank of said bolt from about half of the circumference of a cross section thereof, each of said ridges being substantially crescent-shaped with both end portions thereof gradually sinking into the surface of said shank; and a plurality of second threads having ridges arranged at said regular intervals, each of which ridges extends outwards at right angles to said axis of said shank from substantially the remaining half of the circumference of the cross section thereof, each of said ridges being substantially crescent-shaped with both end portions thereof gradually sinking into the surface of said shank, said second threads being so formed as to be staggered by 1/2 of a pitch thereof from said first threads.

The present invention will now be illustrated, by way of example only, with reference to the accompanying drawings, in which: Fig. 3 is a front elevational view of an embodiment of an anti-loosening bolt according to the present invention; Fig. 4 is a sectional view taken along the line IV--IV in Fig. 3; Fig. 5 is a plan view of the bolt taken in the direction of arrow A in Fig. 4; Fig. 6 is a sectional view of nuts to be screwed on the bolt according to the present invention; Fig. 7 is an enlarged expansion plan illustrating the configuration of the threads on the bolt according to the present invention; and Fig. 8 illustrates the state of two iron plates tightened with the bolt and nuts according to the present invention.

An embodiment of an anti-loosening bolt according to the present invention will now be described with reference to Figs. 3-8.

Referring to Fig. 3, there is shown a bolt 11 having at one end portion thereof a bolt head 1 2 formed integrally therewith. A plurality of first threads 14 and a plurality of second threads 1 5 are formed on the outer circumferential surface of the shank 13 of the bolt 11 in such a manner that the outer circumferential surface of the shank 13 is divided into two by them. As shown in Fig. 4, each of the first threads 1 4 extends outward from about a half of the circumference of a cross section of the shank 1 3. Each of ridges 14' of the first threads 14 is crescent-shaped, i.e. the height of each ridge 14' decreases gradually toward both end portions thereof as if these portions of the ridge 14' sink gradually into the surface of the shank 1 3.As is clear from Fig. 4, the second threads are formed symmetrically with the first threads 14, on the remaining substantially half of the circumference of the cross section of the shank 13. The ridges 14', 15' of these threads 14, 1 5 extend outward at right angles to the axis of the shank 1 3. As is clear from Fig. 3, the plurality of threads 14, 1 5 are arranged at the same intervals. Also, as is clear from Fig. 5, the threads 14, 1 5 are staggered from one another by 1/2 of a pitch thereof in the direction of the length of the shank 13. Namely, the threads 14, 15 are in a so-called zigzag arrangement with respect to one another (refer to Fig. 3).

The bolt 11 of the embodiment of the present invention is formed as described above. When a nut 1 6 shown in Fig. 6, which has a right-hand thread 1 6a, is screwed on the bolt 11, the righthand thread 1 6a come into engagement with ridges 14a, 1 5a, 14b, 1 5b, 14c, 15c. . . . of the threads 14, 15, which are shown in expansion plan in Fig. 7, in that order in the direction of the solid arrows in Fig. 7. When a nut 17 shown in Fig. 6 is screwed on the bolt 1 the left-hand thread 1 7a formed therein come into engagement with ridges 14a, 15a, 14b, 15b, 14c, 15c. . of the threads 14, 1 5 in that order in the direction the dotted arrows in Fig. 7.

Fig. 8 shows two iron plates 18, 1 9 tightened by screwing nuts 16, 17 on the bolt 11 in the above-mentioned manner. When these iron plates 18, 19 or the bolt head 12 receive an impact or vibrations, nut 1 6 having a right-hand thread is urged in the loosening direction, i.e. the counterclockwise direction, to push nut 17, which is in contact with it, to the left. However, when nut 17 is turned to left, it is urged in the tightening direction, i.e. toward the nut 1 6 as mentioned above, to be pressed forcibly against it.

Consequently, the nuts 16, 17 are put in a locked state, so that they are not loosened.

In order to manufacture the bolt according to the present invention, a shank of a bolt material is first set on a lathe and rotated at constant speed.

When a threading tool is then fed in one longitudinal direction, an ordinary helical thread is formed on the shank. When the threading tool is then fed in the opposite longitudinal direction with the shank left rotated in the same direction, the helical thread referred to above are partially cut to obtain the threads shown in Fig. 3.

The process for the production of the bolt according to the present invention is not limited to the cutting process mentioned above; the bolt may be manufactured by using a die or by rolling.

In the bolt according to the present invention described above, threads are formed on the shank having a constant outer diameter. Therefore, the shank of this bolt can be formed without wasting material as compared with a stepped shank of a conventional bolt this kind. The bolt according to the present invention permits the threads to be formed easily, and its cost of manufacture is low.

Moreover, the threads formed on the bolt according to the present invention permits both a nut having a right-hand thread and a nut having a left-hand thread to be screwed thereon.

Accordingly, a nut having a right-hand thread and a nut having a left-hand thread can be tightened on the bolt simultaneously, so that a sufficient anti-loosening effect can be expected. The bolt according to the present invention, in addition to the excellent anti-loosening effect, has another advantage in that the bolt serves both as a bolt having right-hand threads and a bolt having lefthand threads.

Claims

1. An anti-loosening bolt comprising a plurality of first threads having ridges arranged at regular intervals, each of which ridges extends outward at right angles to the axis of the shank of said bolt from about half of the circumference of a cross section thereof, each of said ridges being substantially crescent-shaped with both end portions thereof gradually sinking into the surface of said shank; and a plurality of second threads having ridges arranged at said regular intervals, each of which ridges extends outwards at right angles to said axis of said shank from substantially the remaining half of the circumference of the cross section thereof, each of said ridges being substantially crescent-shaped with both end portions thereof gradually sinking into the surface of said shank, said second threads being so formed as to be staggered by 1/2 of a pitch thereof from said first threads.

2. An anti-loosening bolt substantially as hereinbefore described with reference to Figures 3 to 8 of the accompanying drawings.

3. A combination of a bolt according to Claim 1 or 2, together with a right-hand threaded nut and a left-hand threaded nut.