Note: Descriptions are shown in the official language in which they were submitted.
2 1 ~
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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23473-165
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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23473-165
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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-- 5 --
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
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.. . . . . .
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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-- 8
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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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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-- 10 --
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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