Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~963
T~is invention relates to self-locking fasteners~
Grub screws,locking screws, and the like, are
commonly used to lock a machine part in place. In many
cases, a locking screw is simply tightened so that it is : :
unlikely to work loose. In other cases where the screw .
may be subjected to relatively large temperature variations, ~ ~.
or to mechanical vibration, the locking screw is manufactured
with a peripheral deformation such that when the screw is
fed into a threaded openin~ in a work piece, there is ~
frictional resistance to turning which tends to prevent ~:
release of the screw. However, the force required to enter .:
the screw is not sufficiently different from the force
required to remove it from the openin~ and the screw can be ::
removed without excessive damage to the opening.
Unfortunately, after the screw has been removed `.
several times this ~rictional resistance disappears and a
new set screw must be used. Further, conventional friction~
.
locked set screws must be lubricated to prevent seizure. :~
This diminishes the friction and reduces lock-effect. In
: 20 critical applicatiGns friction locked set screws or other
fasteners are not acceptable and locking elements based on
metallic shear principles (locking w.ire, cotter pins, tub
washers, etc.) must be used.
It is an object of the present invention to
provide an improved self-locking fastener based on the
metallic shear principle.
In its broadest aspect the present invention
provides a fastener for locking a first component to a ~ .
second component, the fastener being adapted to be located
in an opening in one of the components, which opening is ~
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cylindrical in shape and extends about a longitudinal
axis, and the fastener being adapted to engage the
other component. The fastener has a generally C-shaped
transverse cross-section and is adapted to be fitted
into said openlng with said cross-section disposed
transversely with respect to said longitudinal axis of `-~
the opening. The fastener is made of a resilient
material and is radially compressed when located in said
opening so that at least part of the fastener is ~ ~-
resiliently urged against an inner wall of the opening.
A plurality of outwardly projecting barbs are provided
on the said part of the fastener for mechanical engage-
ment with the inner wall of the opening. In use, move- `
ment tending to remove the fastener from said opening
imposes on said barbs, mechanical shear forces tending to
resist such removal of the fastener.
In one aspect, the present invention provides
a self-locking screw which includes a first component
in the form of a screw for insertion in an opening in a
,
second component, and a fastener secured to the screw
component. The screw component has external screw threads
and extends about a longitudinal axis and the opening in
a second component is defined by an inner wall having
internal screw threads complementary to said external
screws threads of the screw component. The fastener has
a generally C-shaped transverse cross-section and has a
~irst end secured to an outer portion o~ said screw
component, and a second end remote from said first end.
The fastener is made of a resilient material and is
arranged to extend generally transversely of and to curve
around said longi~udinal axis of the screw component such
J~)45~63
that at least a part of the fastener is resiliently ~ .
urged against said inner wall of the opening in said
second cornponent when -the screw component is located
in said opening in use. A plurality of outwardly
projecting barbs are provided on said part of the
fastener for mechanical engagement with the inner wall
of the opening. In use, movement tending to remove
the screw component from said opening imposes on said
barbs of the fastener, mechanical shear forces tending
to resist such removal of the screw c~mponent.
In another of its aspects, the invention
provides a spring pin ~astener for locking a first
component to a second component. The fastener is :~
adaptea to be located in an opening in one of said
components, which opening is cylindrical in shape and
extends about a longitudinal axis, and the fastener
is adapted to engage the other component. The ~ :
fastener has a generally C-shaped transverse cross-section .
and is of elongate form, defining a hollow, generally-
cylindrically pin formed with an axial slot. The fastener
is made of a resilient material and is dimensioned such
that it is radially compressed when located in said opening,
whereby the outer surface of the fastener is resiliently
urged against the inner wall of said opening. A plurallty
o outwardly projècting barbs are provided on the said
part of the fastener for mechanical engagement with the
inner wall of the opening. In use, movement tending to
remove the astener from the said opening imposes on said
barbs, mechanical shear forces tending to resist such removal
3b of the fastener.
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It should at this point be noted that the
expression "C-shaped" as used in this specification
and in the claims includes any interrupted circular
shape.
The invention will be better understood by
reference to the accompanying drawings which illustrate
various embodiments of the invention. In the drawings:-
Fig. 1 is a diagrammatic view which illustrates
the principle of operation of a fastener according to the
invention;
Fig. 2 is a plan view of a practical form of
fastener for use in a set screw;
Fig. 3 is a transverse sectional view on line
III-III of Fig. 2;
Fig. 4 is a plan view of a set screw having
spot-welded thereto a fastener of the form shown in Figs.
2 and 3;
Fig. 5 is a transverse sectional view on line
V-V of Fig. 4;
' 20 Fig. 6 is an isometric view of a set screw
; having a fastener spot-welded thereto in somewhat diferent
fashion;
Fig. 7 i.s a view similar to Fig. 6 in which the
astener is secured to the screw by spring pins;
Fig. 8 is an isometric view of a set screw
having an integral fastener;
Fig. 9 is an isometric view o a self-locking
fastener in the form of a spring pin according to the
invention;
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Figs. 10 ana 11 are isometric side views of
other types of spring pin fasteners;
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~045~3
Figs. 12 to 14 are views similar to Figs. 9 to
11 respectively and illustrate modiications of the
fasteners shown in the latter figures;
Fig. 15 is a partial section of a hexagonal nut '
locked with a spring pin fastener;
Fig. 16 shows the nut of Fig. 15 before installa- ~-
tion of the spring pin fastener.
Fig. 17 is a partial cross-section of a hexagonal
bolt head locked with a spring pin fastener;
Fig. 18 is an isometric view of a locked nut
illustrated in Fig. 15;
Fig. 19 is an isometric view''of a locked bolt
illustrated in Fig. 17;
Fig. 20 is an isometric view of an installed
socket head cap screw locked by a spring pin fastener;
Fig. 21 is an isometric view, partly broken away,
of a socket head cap screw, similar to that shown in Fig. 20,
'installed in a counter-bored hole;
Fig 22 is a plan view and Fig. 23 is a cross ,~
section on line X-X of Fig. 21;
Fig. 24 is a side elevation of a punch for use in ' ''~
fitting certain of the spring pin fasteners of the invention;
Fig. 2S is a plan view of a hexagonal nut locXed `
with a spring pin Eastener arranged in an oblique position;
F.~g. 26 is a side view, partly in section, of
the nut of Fig. 25; and
Fig. 27 shows a punch for use in fitting the ,~
spring pin in the arrangement of Figs. 25 and 26.
Reference will first be made to Fig. 1 in explaining
the principle'of operation of a fastener according to the
invention~ Fig. 1 may be considered as a diagrammatic plan
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~5!~3
view. A fastener is indicated at 20 and is shown fitted
in a cylindrical opening 22 in a component 24. Opening
22 has a longi-tudinal axis 26 which extends normal to the
plane of Fig. 1. The fastener 20 i9 coupled to another
component (not sho~n) and serves to lock the two components
together.
The fastener 20 has a generally C-shaped trans-
verse cross-section and is fitted into said opening 22
with its said cross-section disposed transversely with
respect to the longitudinal axis 26 of opening 22. The
fastener is made of a resilient material and, in its
unfitted condition, is of somewhat larger diameter than
the diameter of opening 22. Accordingly, the fastener is
radially compressed when fitted in the opening so that its
outer wall is resiliently urged against the inner wall
of the opening. A plurality of outwardly projecting barbs
28 are provided on the outer wall of the fastener for
mechanical engagement with the inner wall of the opening.
In use, movement tending to remove the fastener from the
opening imposes mechanical shear forces on the barbs, which
forces tend to resist removal of the fastener.
Referenae will now be made to the remaining
figures of the drawings which illustrate the various
practical embodiments of the invention. In the embodiments
of Figs. 2 to 8, the fastener forms part of a set screw
and serves to lock the screw in a screw-threaded opening
in a component which the screw is to be attached.
Figs. 2 and 3 show the fastener prior to attach-
ment to a set screw. The fastener is generally indicated
at 30. In Figs. 4 and 5, the fastener 30 is shown fitted
to the outer end face 32 of a screw 34 having a thread 35,
104~i~63
to form a self-locking set screw. The screw 34 is made Erom a
~errous metal and has a hexagon~l through-socket 36 in its upper
surface. The soc~et may ~e blind in the case of long screws.
As can be seen from Figs. 2 and 4, the fastener
30 is generally C-shaped, having a first end portion 38
by which the fastener is attached to the set screw 34,
and a second, free end portion 40. The free end portion
40 is shaped to define a pair of projections having
vertical edges 42 at the outer end of the fastener. As
can be seen from Figs. 3 and 5, the adjacent portion of
the fastener indicated at 44, is somewhat thickened.
The outer face 46 of this portion is tapered and the inner
face 48 is flat so tha~ a tool can be engaged with the
outer end portion of the fastener for the purpose of re~
leasing the same in the event that the set screw is to
{ be removed from an opening in which it is fitted. A
suitable tool for this purpose is desaribed in U.S. Patent
No. 3,662,804. ;
Adjacent said thickened portion 44 of the fastener
is a series of outwardly projecting barbs 48 which extend
around a substantial portion of the curved outer surface
of the fastener. As can be seen from Figs. 2 and 4 r the
barbs are angled towards the free outer end portion 40 of
the fastener.
Referring now to Figs. 4 and 5, the fastener 30
is spot-welded to the upper surface 32 of the screw 34
along a spot-welded area generally indicated at 50. Although
this area is shown as continuous in Fig. 4, it is, of course,
to be understood that the weld area could be interruPted if ?
required for practical reasons. The shape of the fastener
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~04S9~;3
30 is such as to permit it to be spot-welded in any
orientation with respect to the hexagonal shape of the
socket 36 or to the start of the thread 35 of the
screw 3A. In any event, a clearance C (Fig. 5) is
present between the screw and the remainder of the
fastener remote from end portion 38 to allow movement
of the fastener with respect to the screw. .
In Fig. 4, the minor (root) diameter of the
thread of the screw is indicated in dotted outline at
. 10 52. It will be noted that the fastener 30 is positioned
on the screw such that its outer end portion 40 and the
barbs 48 project outwardly of the said minor diameter.
Accordingly, when the set screw 34 is screwed into a
complementarily internally screw threaded opening in a
machine part or other component, the vertical edges 42
at the outer end portion 40 of the fastener and the barbs
48 engage the crests o the internal thread of the
opening. The positions of the vertical edges 42 and the
angled configuration o~ the barbs 48are such that the
internal thread in the opening deflects the fastener 30
inwardly as the set screw is screwed into the opening,
but the edges and barbs do not mechanically engage in
the thread. When the set screw reaches its fully in
position, the edges 42 and the barbs 44 ancho.r into the
crests of the thread, providing a mechanical engagement
with the said threads. Any movement of the screw in the
anti-clockwise direction tending to unscrew the same
imposes mechanical shear forces on the said edges 42 and
barbs 48, said forces tending to resist such removal of
the fasteners. In other words, the straight edges 42
and the barbs 48 cut into the crests of the internal threads.
:
9S;3
This anchoring ef fect is increased by the asperitie~ ;
at the crests of the internal threaa u.sually left over
from the tap drilling operation by which the thread
was ormed.
The number and shape of the barbs 48 may ~;
vary within practical die limitations.Generally speaXing,
the more barbs provided, the better is the anchoring
effect.
An advantage of making the self-locking fastener
30 separately from the screw facilitates production of ~;
the fastener, for example, by press-punching or by-sintering
techniques using metal powder. The fastener can be
hardened prior to spot welding, which obviates the need to
harden the whole assembly of the screw and fastener. A
further advantage of making the fastener separately i5
that it can be made o~ a non-corrosive metal. In outdoor
ser~ice, the fastener would never corrode and the set
screw would be efEectively locked until the screw itself
disintegrated due to corrosion. Further, a separately -
produced fastener can be attached to any commercial set ~
`:
screw of appropriate type to convert the screw into a self-
locking set screw. Attachment of the fa~tener to the
screw by spot welding is particularly attractive from
this point o view.
Fig. 6 ~shows a set scxew made from a non-ferrous
steel, modified by the addition of a self-locking fastener
o~ the type shown in Figs. 2 and 3, in which the fastener
is attached by thrée spaced welds. Primed reference numerals ;-
have been used in Fig. 6 to denote parts which correspond
with the previous figures. The three spot welds are
indicated at 54.
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S963
Fig. 7 is similar to Fig. 6. Double primed
reference numerals have been used in Fig. 7 to denote
parts which correspond with Figs. 2 to 5. In this case,
the fastener 30" i9 secured to the upper surface 32"
of the screw 34" by three self-locking spring pins
56 which, in effect, act as nails, passing through
aligned openings in the fastener and set-screw. The
pins 56 may be of any of the forms shown in Figs. 12, 13
and 14, and will more specifically be described in ~ -
connection with those figures.
Fig. 8 shows a set screw formed with an integral
self-locking fastener. The body of the screw is indicated
at 58 and the integral fastener portion is denoted 60.
It will be seen that the fastener portion 60 is very
similar in coniguration to the fastener 30 of Figs. 2 and
3. A series o barbs 62 are provided on the fastener and
the outer end of the fastener portion is provided with
projections 64. It will, however, be noted that the barbs
62 and projections 64, in contrast to the previous figures,
have the shape of the external thread on the set screw
body 58. It will, of course, be appreciated that the
edges are of this form because the fastener portion 60
is machined from the ~ screw body. Referring fi.nally
to Fig. 8, it should be noted that the gap between the
fastener portion 60 and the - set screw body 58 is
substantially greater than the clearance C referred to in
connection with Figs. 4 and 5. Accordingly, the set
screw o~ Fig. B will be somewhat longer than the self-
locking screws of the previous figures.
In describing Figs. 2 to 8, reference has been
made to set screws. However, it is to be understood that
-- 11 --
~O~
similar arrangements could be employed for screws Por
other purposes ~e.g. pipe plugs) and that such screws
would be of similar appearance to the se~ screws shown.
Reference will now be made to Figs. 9 to 27
of the drawings in connection with self-Iocking fasteners
in the form of spring pins according to the invention.
Figs. 9 to 11 show three different spring pin
fasteners according to the invention. Like reference
numerals have been used in the respective figures to
denote like parts. In each case, the ~astener includes
a body 66 which has a generally C~shaped cross-section
defining a hollow generally cylindrical pin formed with
an axial slot 68. A series of barbs 70 are provided on
the external surface of each body 66. In each case, the
fastener body 66 is of slightly larger diameter than the
opening in which it is to be fitted. Accordingly, each
fastener is orce-itted into the opening and is radially
compressed in its fitted condition. The barbs 70 scrape
the inner wall of the opening as the pin enters the latter.
In use, movement tending to remove the fastener from the `
opening imposes mechanical shear forces on the barbs, which
forces tend to resist such removal. Further, removal of
such a fastener either aeliberately or as a result of
vibration or thermal cycling would make the barbs spread.
As a result, the fastener would tend to adopt a larger ;
diameter increasing the retaining force.
It will be noted that in Figs. 9 to 11, the barbs
70 axe angled with respect to the longitudinal access of
the fastener in order to facilitate insertion of the
fastener into an opening. However, it is to be understood
that the number of barbs and their location may be varied
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~0~5963
f~om the sp~cific arrangements shown in Figs. 9, 10 and 11.
Figs. 12, 13 and 14 show fasteners having body
portions 66' basically similar to the body portions 66 of
the fasteners shown in Figs. 9, 10 and 11 respectively.
However, in Figs. 12, 13 and 14, each Eastener includes a
flange 72 at its upper end including an angled gap 73 at
the position of the slot 68' in the body portion 66' of
the fastener. The fasteners 56 of Fig. 7 may be of any ;
of the forms shown in Figs. 12 to 14.
Fig. 15 shows how a spring pin fastener according
to the invention may be used to lock a nut 74 to a joint
surface 76. The nut 74 (shown in isolation in Fig. 16) is
modified by the provision of an axial opening 78 aajacent
one of its corners. Opening 78 is countersunk at its
lower end (79). The opening 78 may be drilled or moulded
in during manufacture of the nut. The spring pin fastener
i9 generally denoted 80 in Fig. 15 and may be of any of
the forms shown in Figs. 12 to 14. The fastener may be
factory pre-installed in the axial opening 78 or the
fastener may be supplied separately for insertion by the
i~ user. The fastener is then inserted as will now be
described:-
Fig. 24 shows a punch 82 having a shank 84 and
a handle portion 86 which meet at a shoulder 88. This
;, punch is used to instalI the spring pin fastener 80 in
~I the nut 74 of Fig. 15. The punch is inserted into the
; opening 78 in the nut and is driven into the opening
; until shoulder 88 comes to rest on top of a nut. This
forms a punched hole in the joint surface 76. The depth
of the hole is controlled by abutment of the shoulder 88
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3L0~L5i963
of the punch with the upper surface of the nut. The
lower end of the shank 84 of the punch is formed to
define a sharp end 90 designed to displace the maximum
amount of metal from the joint surface so as to form a
bulge 92 indicated in Fig. 15. This bulge expands into
the countersunk lower end 79 of opening 78 referred to
above. This bulge provides maximum contact between the
nut and joint surface and maximum shear resistance to
removal of the nut. In any event, the fastener 80 is
hammered into the opening 78 until its lower end is ~ully
engaged in ~he indentation formed by the punch. As shown
in Fig. 18, the flange 72 at the upper end of the fastener
80 is preferably spaced above the upper surface of the
nut at this time to permit engagement of the flange by
the tool in the event that the fastener is to be removed.
To maximize the resistance to removal of the
nut, its lower face ~4 is preferably made flat as shown
in Fig. 16 in contrast to the chamfered lower surface
conventionally provided on a nut. ;
The location of the spring pin fastener 80
adjacent the corner of the nut (see Fig. 18~ is such that
the nut can conveniently be engaged by a socket wrench ,7
without inter~erence by the fastener.
It will be appreciated that a nut of the form
shown in Figs. 15, 16 and 18 may be manufactured simply
and economically by sintering at high temperature and
pressure ~rom poWdered metals. The only additional
operation required to form a nut is tapping of the main `~
axial bore.
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~V459~i3
Fig. 17 shows a ~olt having a head 96 and a
shank 98 received in an opening in a component 100.
The bolt head is provided with an axial opening 102
similar to opening 78 in the nut o Figs. 15 and 16
and a spring pin fastener 104 i~ inserted into the
opening in similar fashion to the fastener 80 of the
previous figures. Pin 104 may be similar to pin 80 and
may be installed in similar fashion. It should, however,
be noted that the bolt shown in Fig. 17 cannot conveniently
be manufactured by the sintering method referred to in
connection with the nut. Consequently, the bolt of Fig.
17 would have to be manufactured by conventional methods
and subsequently drilled and countersunk to form the
opening 102.
Figs. 15 to 19 illustrate how nuts and bolts
can be efficiently locked using the spring pin fasteners
of the invention. Figs. 18 and 19 show, in isometric
perspective, the spring pin fasteners in their installed
positions locking a nut (Fig. 18) and a bolt (Fig, 19).
The fasteners are each positioned such that the slot in
the fastener (reference 68' in Figs. 12 to 14) and hence
the gap 73 in ~lange 72 faces in the direction o~
tightening of the nut or bolt as the case may be. The
flanges 72 at the upper ends o~ the ~asten~rs should not
project above the nuts sufficiently to interfere with
use of a socket wrench.
Fig, 20 is an isometric view of a socket head
cap screw 106 formed with a peripheral series of axial
teeth 108. A spring pin fastener 110, which may be of
any of the forms shown in Figs. 12 to 14, is fitted into
an opening in a machine part 112 to which the screw 106
, 15
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~0459~i3
is to be locked. The fastener 110 has a flange 72 at
its upper end which is formed wi~h an angled gap 74 of
a shape complementary to the shape o the teeth 108.
The gap 73 is positioned to enyage one of the teeth,
whereby the screw 106 is locked against turning.
Fig. 21 shows the cap head screw 106 of Fig.
20 located in a hole 118 in the machine part 112. As
in Fig. 20, the screw 106 is locked by a fastener 110
arranged as in Fig. 20. A contersunk portion 120
(See Fig. 23)- is provided at the lower end of the hole ;
118 in the machine part 112. This countersunk portion
provides clearance to permit removal of the spring pin
fastener at appropriate times. This may be effected by
a screwdriver, a small crowbar or by a special tool ; `
as referred to above.
Figs. 25 and 26 show respectively a plan view
, and a partially sectioned side elevation of a nut 122
formed with a hole 124 which extends obliquely from one ~`
corner of the nut and penetrates the axial bore 126 of
the nut. It will be noted that the hole 124 will not
weaken the nut because the hole is located in the upper
;~ portion of the nut, whereas it is the lower portion which ~;
carries the load. A punch such as that shown at 128
in Fig. 27 i5 inserted into the hole 24 and is used to
provide an indentation in the bolt or other threaded
component inserted into the bore 12b of the nut. A
spring pin astener such as that indicated at 130 is
.
then inserted into the hole 124 and driven home into the ~
indentation formed by the punch 128. ~ `
Although in the embodiments of Figs. 9 to
27 reference has been made to a single spring pin fastener
- 16 -
~04S963
only for locking a bolt or nut, it is of course, to be
understood that more than one such fastener could be
employed in a single nut or bolt head if required. Further,
although the drawings show hexagonal nuts and bolt heads,
it is to be understood that other ~orms of nuts (e.g. square,
rectangular, round) may be manufactured with one or more
axial or inclined openings.
This ~ethod of locking a nut or bolt described
above avoids the need for substantial lateral clearance
around the nut or bolt head required when nuts or bolts
are locked by conventional methods employing cotter pins
or locking wire. In turn, this allows nuts and bolts to
be located closer together than otherwise would be possible,
permitting overall weight and size reductions.
Self-locking screws and spring pin fasteners
such as those described above have the advantage that they
can be of shorter length than conventional self-locking
screws and spring pins. This permits design of lighter
and less bulky equipment than is currently possible. For
20 example, in nuclear plants the predominant shape is a tube
and its joint, either in-line joint or "T" joint. Joînts
must be reliably locked because of vibratory or varying
temperature services. Presently used locking methods
require substantial lateral workin~ clearance for use
of tools and hands. To lock nuts, bolts or screws with
locking wire, or cotter pins, space at the side of the
fasteners must be available to drill a hole with an
electrlc drill. For example, to lock the cap screw with
a locking wire a side clearance for both hands and pliers,
3~ to twist the wires, must be available. Self-locking screws
and spring pins, according to the invention, being very
17
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~0459~3
short, permit the use of much thinner tubes and slimmer
joints.
The quality inspection of locked screws
according to the invention, would be ~asy, instant and -~
meaningful. By contrast, it is dif~icult to inspect
the installation and locking integrity of nuts, bolts or
screws either locked with locking wire or with cotter pins
without removing the locking element first - to test the
~ ,
torque - or to use dental mirror to inspect proper locks
in inaccessible spots.
Finally, it should be noted that fasteners
according to the invention can be locked or unlocked from
a distance. The remote handling of set screws is possible
by means of a tool dlsclosed in U.S. Patent No. 3,662,804.
A similarly constructed tool may be used or remote
installation or removal of proposed spring pin fasteners.
~ . . .
Remote handling becomes an important feature when dealing
with hostile environments such as radiation, high-or-low
temperature, vacuum, oxygen-less space, inaccessible spaces, `
2~ stc.
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