Note: Descriptions are shown in the official language in which they were submitted.
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STRUCTURE FOR PREVENTING THE LOOSENING
OF A TIG~TENED SCREW ASSEMBLY
BACKGROUND OF THE INVENTION
The present invention relates generally to a structure
for preventing the loosening of a tightened screw assembly, ;
even when the assembly is only loosely tightened.
There are many types of threaded screw assemblies for
fastening two memberes to each other, such as a threaded male
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screw and associated female member. Equally well known are
assemblies for clamping a third member therebetween based on
; the tight engagement between a male screw member and an
;~ associated female member.
To prevent the loosening of such fastened screw
assemblies, one or more of the following techniques are
commonly employed: securing two nut members to a single bolt
member in a so-called double screw engagement, disposing a
spring washer between the nut and bolt members,
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placing a tack or wire hook through the bolt member to prevent
the nut member from rotating, or using a split pin type bolt
having a tapered shank portion longitudinally split into two
parts to generate a resilient force opposing a compressive
forc- created, when the male member engages the female member.
In general, for such type of fasteners, securely tightening
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~ the male to the female member produces sufficient friction to -~
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21 331~3
prevent the disengagement of the nut from the bolt.
Some applications of threaded fasners, however, require
a bolt or screw member that is loosely rather than securely
tightened to the female member. An example of this is a screw
5assembly adapted to a joint pivot or hinge rod assembly of,
for example, a pair of scissors. A loosely tightened screw
assembly allows the scissors to be easily manipulated while
at the same time preventing the scissors from becoming too
loose for efficient cutting.
10Unfortunately, some applications requiring loosely
threaded screw assemblies such as scissors can not utilize the
above memtioned common techniques for preventing the loosening
of the screw assembly. For example, double screw engagement
as well as spring washers are impractical for scissors or
15other similar type applications. Similarly, tacks and wire
hooks placed through a bolt member are poorly suited to
prevent the disengagement of scissors halves. of the above
memtioned widely used techniques used to prevent the
disengagement of screw assemblies, the only applicable
20technique is the split pin type bolt having a tapered shank
portion longitudinally split into two parts.
The disadvantage of using bolts having tapered shank
portions for applications requiring loosely tightened screw
assemblies is that, until the tapered screw is fully or
25securely tightened, the screw's threads will not fully engage
the threads of the associàted female member. Given conditions
where a minimal tensional force is applied to the male and
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female member~, the screw assembly tends to become disengaged.
Conse~uently, tapered shank type screw assemblies, as well as
the other above mentioned techniques used to prevent the
loosening of screw assemblies, are poorly suited to loosely
tightened screw assemblies.
SUMNARY OF THE INVENTION
Accordingly, it is a primary objective of the present
invention to provide a structure for preventing the loosening
of a threaded screw assembly that has a wide range of
10 applications and which is not limited by the disadvantages
associated with conventional techniques.
To achieve the foregoing and other objects and in
accordànce with the propose of the present invention, an
improved structure is provided, for preventing threaded screw
15 type fasteners from becoming loose. The screw assembly of the
present invention includes a first member having a recess
defined by a first threaded peripheral surface, and a second
member including a projection having a second threaded
peripheral surface, whereby the second member can engage the
20 first member.
The improved structure comprises at least one engaging
recess formed on either the first or second peripheral
surfaces, and at least one spring clip provided in the
remainder of the first and second members. A portion of the
25 spring clip projects from the peripheral surface of the member
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in which the clip is provided, and couples with the engaging
recess provided on the associated member's peripheral surface.
The projecting portion of the spring clip is retractable into
the clip providing member to allow its member to disengage
from the engaging recess.
It is preferable that the engaging recess comprises a
groove extending substantially along a direction axial to the
first and second periferal surfaces. Accordingly, the contact
area for the engagement between the engaging recess and the
spring clip increases, and produces a tight engagement
therebetween.
BRIEF DESCRIPTION OF THF DRAWINGS
The features of the present invention that are believed
to be novel are set forth with particularity in the appended
claims. The invention, together objects and advantages
thereof, may best be understood by reference to the following
description of the presently preferred embodiments together
with the accompanying drawings.
Figs. 1 through 3 show a first embodiment according to
the present invention: ~
Fig. 1 is a perspective view showing a bolt and a nut; ~ -
Fig. 2 is a cross-sectional view of the bolt which is ~;
longitudinally cutaway; and ;
Fig. 3 is a plan view of the nut. --~
Figs. 4 and 5 show a second embodiment according to the
21~3183
present invention:
Fig. 4 is a partly cross-sectional view of the bolt; and ~;
Fig. 5 is a plan view of the nut.
Figs. 6 and 7 show a third embodiment according to the
present invention:
Fig. 6 is a front view of the bolt; and
Fig. 7 is a cross-sectional view of the bolt.
Fig. 8 is a perspective view showing an another
modification according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS ,
... .
The first through third embodiments according to the
present invention will now be described referring to the
accompanying drawings.
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The first embodiment as shown in Figs. 1 through 3
employs a combination of a bolt 1 and nut 2. The bolt 1
includes a head 11 and a shank portion 12, similar to a
conventional bolt. The head 11 includes an engaging portion
for turning the bolt, e.g., a hexangular recess 13 for
engaging with an Allen Wrench. The shank portion 12 includes
threads 16 which are formed around the peripheral surface
tbereof, and a recess 14 which is longitudinally formed along
the shank portion 12 in such a manner that it splits the shank
portion 12 into two parts.
Further, a spring clip 15 is fixed to the shank portion
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12 at the upper portion of the recess 14. Although a trunk
portion of the clip 15 projects outward beyond the peripheral
surface of the shank portion 12, the trunk portion can be
depressed into the recess 14. When the spring clip 15 is
depressed within the recess 14, the clip 15 exerts an urging
force outward due to its own spring action.
The nut 2 comprises a main body 21 having a through hole
22 formed therein. Threads 24 as well as londitudinal grooves
23 (six grooves in this embodiment) are formed around inner
peripheral wall of the through hole 22. Each of the grooves
23 extends along a central axis of the nut. When the bolt 1
and nut 2 are engaged with each other, the spring clip 15 fits
into one of the grooves 23.
The just fitting of the clip 15 into one of the grooves
23 allows an operator to sense the favorable engagement
through the click of the bolt 1. As the bolt 1 turns, the
spring clip 15 is pushed into the longitudinal recess 14. The
resiliency of the pushed spring clip 15 results in resistance
when the bolt 1 is turned. The resistance contributes to
prevent the loosening or disengagement of the bolt from the
! inut.
The second embodiment of the present invention as Qhown
in Figs. 4 and 5 illustrates a different securing arrangement
of spring clip and bolt than described in the first
embodiment. As shown in Fig. 4, an insertion pit 17 is formed
at the cente~ of a shank portion 12 of a bolt la. The shank
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portion 12 includes a longitudinal recess 14 formed at the
lower half portion thereof while the spring clip 15a is formed
from wire having an elastic or resilient property. The
proximal end of the clip 15a is securely fitted into the
insertion pit 17, and the remaining portion of the clip 15a
projects beyond the peripheral surface of the shank portion
12. According to this design, the spring clip 15a in the
second embodiment has superior and stronger resiliency than
that of the spring clip 15 described in the first embodiment.
As shown in Fig. 5, a nut 2a includes a polygonal through
hole 22a, here shown as a hexagon, which is simply threaded
by means of a tap. According to this embodiment, it is easy
to form a male threaded portion 25 including engaging groove
portions 23a which corresponds to the longitudinal grooves 23
in the first embodiment. ~
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Figs. 6 and 7 illustrate a third embodiment according to
the present invention wherein a bolt lb having a shank portion
30 incorporates a longitudinal slit along the shank portion
of the bolt lb and an insertion cavity 141. A spring clip 15b
is formed from resilient wire and bent in a hooked shaped
fasion as shown in Fig. 6. The clip 15b is inserted into the
insertion cavity 141 so that the side portions of the clip 15b
project beyond respective peripheral edges of the bolt shank
30, as shown in Fig. 7.
When the bolt lb engages with the nut shown in Figs. 3
or 5, the projected portions of the clip 15b couple with the
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engaging grooves 23 or 23a. Thye progressive clicking of clip
15b into grooves 23 or 23a, during the threading engagement
or disengagement of bolt lb and associated nut, allows for
tachle confirmation that the bolt and nut assembly is
prevented from disengagement.
Although only three embodiments of the present invention
have been described in detail herein, it should be apparent
to those skilled in the art that the present invention may be
embodied in many other specific forms without departing from
the spirit or scope of the invention. Particularly, it should
be understood that the following modifications are applied to
the present invention.
Engaging grooves may be made in a male screw member, and
a spring clip may be provided in a female member, as shown in
Fig. 8. Additionaly, a plurality of spring clips may be
provided on one of a male screw and an associated female
member. ~ t
Therefore, the present examples and embodiments are to
be considered as illustrative and not restrictive and the
invention is not to be limited to the details given herein,
but may be modified within the scope of the appended claims.
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