CA2105574A1 - Screw element which can be secured against unscrewing - Google Patents

Abstract

Abstract A screw element (100) comprises a body (3) having an internal thread (9) which can be screwed onto a screw (1). An axial protrusion (10) of the body (3) exhibits a spiralled outer peripheral surface (17), on which there is disposed a correspondingly spiralled inner peripheral surface (27) of a clamping ring (20). As a result of the clamping ring (20) being twisted relative to the body (3), the protrusion (10) is clamped tight non-positively on the screw (1) and the screw element (100) thus secured against unscrewing. (Fig. 1)

Description

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Screw element which can be secured against unscrewing For screw element~ such a~ nut~ and the like, various de~igns are known for the ~ecurement again~t unscrewing of the tightened ~crew connection under the axial forces and, where appropriate, vibrations which occur. The ~imple-qt embodiment is the lock nut, which i~
limited on an axial ~ide in a crenellated shape, the indentations between the crenellation~ being able to be brought into coincidental arrangement with a cro~s-bore of the ~crew and a cotter pin being ~tuck through transversely. The drawback in thi~ 18 the need to apply a cros~-bore to the screw and, in particular, the fact that the ~ecurement again~t unscrewing i~ po~ible only in certain rotation position~ of th~ ~arew element, namely when one of the indentation~ between the cre-nellation~ coincides exactly with the cross-bore in the screw~ A further method of ~ecuring a ~crew connection again~t unscrewing is the fltting o~ a 3pring ring. This dig~ with one cutting edge into the under~ide of a nut, with the other cutting edge into the counter-workpiece and, by the orientation of the cutting edge~, prevent~
tho nut from un~crewing. When ~igh~en~ng occurs, the sur-face~ on whieh the cutting edges of the ~pring ring are engaged become damaged.
A deliberate loo~ening of the secured ~crew connection i~ only po~ible against the action of the ~pring xing and accompanied by greater destruction~ of the engagement surfaces of the ~aid ~pring ring. La~tly, there are ~crew elemente in the ~orm of ~o-ealled check : . . . . . . . .. . . . .
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nuts, which exhibit on their bearing surface radial cutting edge~ in the style of a file cut, whiah cutting edges claw into the counter-surface in a similar m~nner to the ca~e in respect of the ~pring ring. The drawbacks are also of cour~e the same, the notches formed being a pos~ible~ ~tarting point for fatigue fractures ("Konstruktion & Elektronik~ magazine (1991), I~sue 4 of 20.2.1991, paye 4; EP-B1 290 967).
The object of the invention is to provide a ~crew element which can be secured again~t unscrewing, in which no ~pecial ~haping whatsoever ha~ to be pre~ent on the ~crew and in which the bearing ~urfaces do not become damaged by the securement procedure.
Thi3 object i~ achieved according to the inven-tion by a ~crew element according to Claim 1.
The screw element i~ tightened in the conven-tional manner until the de~ired ten~ion is reached in the ~crew connection. The clamping ring i~ then twi~ted on the ~piral ~urface, a~ a re~ult of which the bu~h-like protru~ion, which is naturally of corre~pondingly thin-walled configuration, i~ radially compre~Yed and 3ettle~
in po~ition with the internal thread on the ~crew, 50 that a non-po~itive blocking again~t un~cr~wing i~
achieved on the screw. Only a relatively ~mall reciprocal twi3ting of the body of the ~crew element and the clamping ring i~ required to provoke the blocking.
The actual clamping connection remai~ unaffected .
by thi~ procedure, ~ince the function~ of the actuation of th~ ~crsw element in order to obtain the deeired axial .. ' . . ,' ' .. . . . .
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force in the screw, on the one hand, and to obtain the securement against unscrewing of the screw element are totally separate from each other. The screw element can be tightened without the bearing surfaces of securing elements becoming damaged and without supplementary moments having to be applied for the actuation or activation of securing means.
In addition, as a result of the radial compression of the bush-like protrusion provided with the internal thread, the engagement of the thread or of its bearing component is increased, so that, yi~en the same axial forces of the screw connection, the local surface compression can be reduced.
The use of spiral surfaces to obtain a radial blocking is taken per se from GB-Patent Specification 293 122. In this, two rings, disposed one above the other, are present, one of which is seated with its cylindrical inner peripheral surface on a shaft and the other of which comes to bear with its cylindrical outer peripheral surface in a corresponding bore of an outer structural part. The mutually facing peripheral surfaces of the two rings are spiralled in a cross section perpendicular to the axis of the shaft. If the outer structural part is twisted relative to the shaft, the two spiralled rings, due to the frictional relationships, are also reciprocally twisted on their spiral surface, as a result of which the blocking of the outer structural part on the shaft is realized.
From GB-A 23 812 (1911), an arrangement is known upon which preamble is based and in which spiral surfaces are likewise -used to obtain a radial blocking. In this case, however, the element having the spiral surfaces is a part which is separate .~ . . , , ~ --, , - . ..
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from the "body" and which is rotated, in the style of a counter-nut, counter to the body. The body thus has only a relatively short thread and, when the element having the spiral surfaces is tightened, the axial tension of the thread which is initially set on the body is altered.
The screw element forms, in its simplest embodiment comprising body, bush-like protrusion and clamping ring, the basic form of a check nut, which, according to claim 2, is configured on the outer periphery of the body with a shaping for the application of a turning tool, for example exhibits on the periphery longitudinal grooves or radial bores for the applica-tion of a sickle spanner or, conventionally, is hexagonally configured.
A corresponding shaping can also be exhibited, accord- -ing to claim 3, by the clamping ring.
In this way, the body of the screw element and the clamping ring can be effectively reciprocally twisted at high torque, two turning tools being simultaneously applied, in order to generate the clamping effect on the screw.
In order to ensure, in the reciprocal twisting of the body of the screw element and of the clamping ring, that not too much of the applied torque is used up for the mere compression of the bush-like protrusion, for the purpose of surmounting the play on the screw, a longitudinal slot according to claim 4 is advisable, which considerably increases the deformability of the bush-like protrusion in the radial direction without substantially reducing the stability in the peripheral direction and hence the grip of the securement.

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- 4a -23~73-165 An illustrative embodiment of the invention is represented in the drawing, in which:
Fig. 1 shows a longitudinal section, passing through the axis, through a screw element;

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Fig. 2 shows a ~ection according to the line II-II in Fig. 1.
The screw element, denoted in it~ entirety by 100 in Fig~. 1 and 2, constitute~ a check nut, which can be screwed onto a screw or ~crew ~pindle 1 (indicated in Fig. 1 only in dash-dot representation) having an axi~ 2.
The screw element 100 compri~es a body 3 in the ~hape of a thick di~k 4, the thickne ~ of which, in the reproduced illustrative embodiment, measures about one-quarter of the diameter. The outer periphery 5 of the di~k 4 i~ -cyli~drical and exhibits four longitudinal grooYe~ 6 which are di~tributed uniformly over th~ periphery and to which a sickle spanner for turning the ~crew element 100 - can be applied.
On the (in Fig. 1) right-hand flat side of the disk 4, the body 3 po~ee~e~ an elevation 7 of circular cro~ section havin~ an outer lim~t ~rface 8 whLch is perpendicular to the axiB 2 and forms the bearing 3urface of the ~crew element 100 with which the sald screw element comes to bear a~ain~t a counter-surface on a structural part relative to which the ~crew 1 i~ to be braced. ' The disk 4 i~ pro~ided with an internal thread 9, which can be screwed onto the coxresponding external thread of the ~crew 1.
The thread 9 continue~ through a bush-like pro trusion 10 coaxial to the axi 2, which pro~rusion i~
provided on that flat ~ide of the di~k 4 facing away from the slevation 7. The thread 9 provide~ ~upport there~or~

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on the screw 1 over the total length of the body 3 and of the protrusion 10. The thread pitch i~ dimen~ioned relative to the thickne~s of the body 3 such that the body 3 alone accommodate~ a plurality of thread tUrn9.
The axial bu~h-like protru~ion 10 exhibit~ in a plane passing through the axi~ 2, at one or more points distributed over the periphery, a radially continuous longitudinai slot 11 which facilitates the radial com-pression of the protrusio,n 10.
Thie radial compresqion i~ brought about by a clamping ring 20, which i8 di~po~ed rotatably on the outer periphery of the axial pro~ru~ion and i~ unslotted and i3 provided with a cros~ section which i0 large in comparison with the protru~lon, since it ha~ to ab~orb the ring ten~ile stres~e~ generated by the radial force~.
The axial protrusion 10 protrudes over the clamping ring 20 toward~ that ~ide which is remote from the body 3 ~nd po3~e~es there, on the outside, a peri-pheral. ~roove 12 for the reception of a ~nap ring 13, by means of which the alamping ring, which i3 loo~e in the unbraced ~tate, i~ held fa~t on the protrusion 10 and thue remain~,captively connected to the body 3.
The outer periphery 15 of the alamping ring 20 i~
also cylindrical in the illustrative embodimen~ and po~aes e~, at point~ di~tributed over the periphery, longitudinal grooves 16, in which a sickle spanner'can be engaged in order to tW19t the clamping ring 20 relative to the body 3.
The clamping arrangement formed by the protru~ion , '' ~ ~ ' .. . . . . .

10 and the clamping ring 20 i8 explained in detail with reference to Fig. 2. In the ~ectional representation, an imaginary cylindrical surface 14 i3 indicated in da3h-dot representation with the central point on the axi~ 2. The outer peripheral surface 17 of the bush-like protrusion 10 iR formed by a spiral surface 18 coaxial to the a~is 2, the generating line~ of which spiral surface are parallel to the axis 2. The inner peripheral ~urface 27 of the clamping ring 20 is formed by an identical spiral ~urface 28, which bears from the outside upon the spiral surface 18. The two spiral ~ur~ace~ 18, 28 lie, in the fir~t two quadrante of the cro~s ~ection of ~ig. 2, outside the lmaginary cylindrical surPace 14, intersect the spiral surface 14 in the "8iX o'clock" location and lie, in the la~t two quadrant~, within the cylindrical ~urface 14. The local radiu~ of the Rpiral surface 1~
decline~ clockwise, from a point 19 of greatest radius according to Fig. 2, in an angle-prsportional manner over almost 360 and spring~ back again, at a point 21 of l~a~t radlus on a tran~ition ~urface 22, to the greatest radiu~. The inner peripheral eurface 27 of the clamping ring 20 ie corre~pondingly ~haped, i.e. the radius diminishes clockwisa, from a point 19' of greate~t radiu~, ln an angle-proportional manner up to a point 21' of least radlu~, whereupon the inner peripheral ~urface 27, in a tran~ition surface 22~ in a narrow angular range, ~prinys back again to the point 19' oP greate~t radiu~. The ~ize of the pitch of the spiral ~urface~ 18, 28 in the peripheral dixectlon i~ aho~en ~uch that it .
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lies in the self-locking range and the clamping ring therefore, once tightened, no longer turns back witho~t external torque. Given a radiu~ differential of 2 mm in respect of a 50 mm diameter, a wedge i8 produced, in the developed view, having the gradient ~ 2 : 150, which iB
equivalent to le~s than one degree, the limit angle of the self-locking being about 7 in the ca~e of ~teel on ~teel. In the example, the ~piral surfaces 18, 28 thus lie well within the elf-locking range, which simul-taneously mean~ that the conver~ion of the torque applied to the clamplng ring 20 into radial clamping force ia effected highly efficiently.
In Fig. 2, the clamping arrangement 10, 20 i~
repre~ented in ~ not yet fully braced state. In a fully unbraced 6tate, the transition surfaceY 22, 22' are yet more adjacent to each other in the peripheral direction.
The function of the bracing can be illustrated by consi-dering that point 19 of t~e bu~h-like protrusion 10 which exhibits the greate~t radius of the spiral surface 18. In the ~vent o~ a clockwise movement of thi~ point, the clamping ring 20 according to Fig. 2 being held fa~t" the ~aid point bear~ successiyely again~t points of the ~piral ~urface 28 which exhibit a ~maller and ~maller radiu~. The point 19 i~ th~reby forced radially inward~.
The equlvalent applies to all other po~nt~ of the periphery, with the exception of the zone~ which are left free between the points 19 and 21'. In this way, the axial protru~ion 10 is uniformly compre~ed in the radial direction and i~ clamped tight non-po~itively on the .... .
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g screw 1. As a result, the screw element 100 can no l~nger be twi~ted and maintains its ro~ation po~it~on once reached.
Where the diameter of the screw 1 measures from 30 to 50 mm as in the e~ample already mention~d, the radius differential of the point~ 19, 21 can amount to around 2 mm. By twi~ting the clamping ~ing 20 clockwise by 36 relative to the bush-like prokru~ion 10, a radius tolerance of 0.2 mm can thus be bridged, which in the majority of cases i9 sufficientO The tightening-rotation stroke~ which e~ter into consideration will in no instance have to exceed 45. If the clamping ring 20 were twisted correspondingly relative to the axial protrusion 10, the transition surfac2 22' would be located approxima~ely at the position 22~' indicated in da3hed representation in Fiq. 2.
In operation, the ~crew element forming a check nut can be tightened by the body 3 being.twi~ted up to the point where the limit surface 8 come to bear against a counter-surface. A torque giYing ri~e to the ten~ile ~tres~ in the screw 1 i~ then applied to the body 3, by mean~ of a ~lckle spanner for example, which engage~ in the grooves 6. In carrying out thi~ tighten~ng, no supplementary moments what~oever have to be applied for the securement of the screw element 100, i.e. the entire torque applied at the periphery 5 i8 used to promote the bracing of the ~crew 1.
Once the bracing has been achieved, the twisting of the clamping ring 20 ls ef~ected u~ing a ~imilar ~ool, ,... ~ . ~ . . ~ . -.. . .
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which engages in the ~rooves 16 of the clamping ring 20.
The bush-like protrusion lO i~ thereby radially compre~sed in the manner d~scribed and braced non-posi-tively on the screw 1. In carrying out this bracing, counter-holding pressure can, where necessary, be applied to the body 3 using a further turning tool, in order to prevent the achieved bracing of the screw 1 from being altered.
The securement of the screw element 100 is effected totally within thi~ element, without any engagement on the structural part forming the counter-bearing for the limit 3urface 8 or on the screw 1 and without the securement being dependent upon the material sf this counter-aurface.
The available length of the thread 9 is increased by the bush-li~e protru~ion 10 and, as a re~ult of the radial compres~ion in the region of ~he axial protrusion 10, the engagement of the ecrew thread i5 also improved.
The body 3 does not have to be a pure nut, as in the represented illu~trative e~bodiment, but can al~o it~elf be a structural part which performs a further function/ Additionally, in the example, only one protru~ion 10 is provided, having a clamping ring ~0 on one ~ide, although a double-~ided con~truction and a con~truction having two or more cl~mping rings on one ~ide may al80 enter into con3ideration.

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Claims (4)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Screw element (100) which can be secured against unscrewing having a disk-shaped body (3), having a continuous internal thread (9) in the body (3), of which a plurality of thread turns are accommodated in the body (3), having a bush-like part possessing an internal thread, which part is concentric to the internal thread (9) and is provided on at least one side of the body (3), having a spiral surface (18), which is disposed on the outer peripheral surface (17) of the bush-like part, coaxial to the axis (2) of the internal thread (9), and is formed from generating lines parallel to the axis (2) and exhibits, in the peripheral direction, a pitch which lies in the self-locking range, and having at least one clamping ring (20), which is disposed on the spiral surface (18), is rotatable and is undivided in the peripheral direction and the inner peripheral surface (27) of which is a spiral surface (28) corresponding to the spiral surface (18) of the bush-like part and bearing upon the said spiral surface (18), whereby, upon the rotation of the clamping ring (20), the bush-like part can be radially compressed and the screw element can be clamped tight on an externally threaded part (1) screwed into the internal thread (9), characterized in that the bush-like part is formed by a protrusion (10) of the body (3), by which the internal thread (9) is continued.

2. Screw element according to claim 1, characterized in that the screw element (100) is configured as a nut having a shaping (6), provided on the outer periphery (5) of the body (3), for the engagement of a turning tool.

3. Screw element according to claim 1 or 2, characterized in that the clamping ring (20) exhibits, on the outer periphery (15), a shaping (16) for the engagement of a turning tool.

4. Screw element according to one of claims 1 to 3, characterized in that the body (3), at least in one longitudinal region of the bush-like protrusion (10), is longitudinally slotted in a plane passing through the axis (2).