U.S. patent application number 09/984297 was filed with the patent office on 2002-03-07 for fastening system.
This patent application is currently assigned to ITW Automotive Products GMBH & Co. KG. Invention is credited to Jahnke, Klaus, Jakob, Andreas, Kirchhoff, Peter, Schneider, Mario.
Application Number | 20020028121 09/984297 |
Document ID | / |
Family ID | 8079352 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020028121 |
Kind Code |
A1 |
Jakob, Andreas ; et
al. |
March 7, 2002 |
Fastening system
Abstract
A fastening system with a screw which comprises a screw head and
on a screw shank a thread which with respect to the pitch and the
flank angle is matched to the formation of a thread in a bore of a
plastic material, and at least one axially extending deepening on
the thread root, and with a plastic material with a bore into which
the screw may be threaded whilst forming a thread and/or with a
clip with two clip bows and a clip back which connects these and
which comprises a through bore traversing the clip bows, with a
thread for rotating in the screw and at least one resilient lug
aligned radially to the axis of the through bore, for latching into
the at least one deepening of the screw when this is rotated into
the through-bore of the clip.
Inventors: |
Jakob, Andreas; (Hemer,
DE) ; Jahnke, Klaus; (Hemer, DE) ; Kirchhoff,
Peter; (Wickede, DE) ; Schneider, Mario;
(Landau, DE) |
Correspondence
Address: |
LOWE HAUPTMAN GILMAN & BERNER, LLP
Suite 310
1700 Diagonal Road
Alexandria
VA
22314
US
|
Assignee: |
ITW Automotive Products GMBH &
Co. KG
|
Family ID: |
8079352 |
Appl. No.: |
09/984297 |
Filed: |
October 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09984297 |
Oct 29, 2001 |
|
|
|
09659076 |
Sep 11, 2000 |
|
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Current U.S.
Class: |
411/294 |
Current CPC
Class: |
F16B 35/041 20130101;
F16B 25/00 20130101 |
Class at
Publication: |
411/294 |
International
Class: |
F16B 039/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 15, 1999 |
DE |
299 16 793.3 |
Claims
1. A fastening system with a screw (1) which comprises a screw head
(2) and on a screw shank (3) a thread (4) which with respect to the
pitch (h) and the flank angle (.alpha.) is matched to the formation
of a thread in a bore (9) of a plastic material (7), and at least
one axially extending deepening (5) on the thread root, and with a
plastic material (7) with a bore (9) into which the screw (1) may
be threaded whilst forming a thread and/or with a clip (17) with
two clip bows (18, 19) and a clip back (20) which connects these
and which comprises a through bore (23', 23") traversing the clip
bows (18, 19), with a thread (24) for rotating in the screw (1) and
at least one resilient lug (25) aligned radially to the axis of the
through bore (23', 23"), for latching into the at least one
deepening (5) of the screw (1) when this is rotated into the
through-bore (23', 23") of the clip (17).
2. A fastening system according to claim 1, in which the thread (4)
of the screw (1) has a flank angle of (.alpha.) of about 20 to
40.degree., in particular of about 30.degree..
3. A fastening system according to claim 1 or 2, in which the
thread (4) of the screw (1) has a pitch (h) of about 1.5 to 3.5 mm,
in particular of about 2.2 mm.
4. A fastening system according to one of the claims 1 to 3, in
which the screw (1) comprises several deepenings (5) on the thread
root arranged uniformly distributed over the circumference of the
screw.
5. A fastening system according to one of the claims 1 to 4, in
which the at least one deepening (5) is aligned parallel to the
screw shank (3).
6. A fastening system according to one of the claims 1 to 5, in
which the at least one deepening (5) has a symmetrical cross
sectional shape.
7. A fastening system according to one of the claims 1 to 6, in
which the at least one deepening (5) has an asymmetrical cross
sectional shape, which is designed such that the screw (1) on
rotating in slides on the lug on a flank inclined more heavily the
axis of the lug (25) and on loading in the counter direction
presses with a flank inclined less to the axis of the lug (25)
against the lug (25).
8. A fastening system according to one of claims 1 to 7, in which
the plastic material (7) is a plug for fastening the screw in a
bore of a carrier material.
9. A fastening system according to one of claims 1 to 7, in which
the plastic material is a carrier material or a section of the
carrier material.
10. A fastening system according to one of claims 1 to 9, in which
one clip bow (19) of the clip (17) is a spring bow which in the
unloaded condition is inclined to the other clip bow (18) and with
a clip (17) sled onto a flat carrier material is pivoted somewhat
away from the other clip bow (18).
11. A fastening system according to claim 10, in which the clip bow
(19) designed as a spring bow at the free end comprises a
suspension lug (21) bent away from the oppositely lying clip bow
(18), for simplifying the sliding onto a flat material.
12. A fastening system according to one of claims 10 or 11, in
which a clip bow (19) on the side facing the other clip bow (18)
comprises barbs (22', 22") for position securement on a flat
material.
13. A fastening system according to one of claims 1 to 12, in which
the clip (17) comprises several lugs (25) arranged symmetrically
about the through-bore (23', 23").
14. A fastening system according to one of claims 1 to 12, in which
the at least one lug (25) comprises an end section (26) converging
towards the free end, for the engagement into the at least one
deepening (5) of the screw (1).
15. A fastening system according to one of claims 1 to 14, in which
the at least one lug (25) is bent out of the flat material of the
clip (17).
16. A fastening system according to claim 15, in which the at least
one lug (25) is bent out of the edge regions of the two clip bows
(18, 19) and the clip back (20).
17. A fastening system according to one of the claims 1 to 16, in
which the clip (17) is of metal, in particular a metal sheeting.
Description
[0001] This invention relates to a fastening system. It serves for
attaching a structural component to a carrier material.
[0002] It is been known already to insert a plug into a bore of a
carrier material and to locate it therein by friction or securing
it in place. In such a case, the plug has a bore into which a screw
is rotated in order to fasten the structural component to the
carrier material. The plug may then be located in the carrier
material by forcing it in or latching it in by hinged feet or
widening it by means of the screw. In known plastic plugs, threads
are formed in the bore by rotating the screw in, e.g. by
thread-molding or thread-cutting. For this purpose, the screw has a
flank angle, which is comparatively acute as compared to screws for
metal sheeting or metric-thread screws and typically is 30.degree..
In addition, such screws have a pitch which is large as compared to
screws for metal sheeting or metric-thread screws and may be 2.24
mm, for example.
[0003] The aforementioned fastening may be employed particularly
for flat carrier materials which have a through-bore to receive a
plug. Such a fastening is used especially in automobile
manufacture, e.g. for attaching guide strips or panelings to the
body.
[0004] In addition, fastenings for structural components to flat
carrier materials are known already, which include a metallic screw
and a metallic clip. The metallic screw typically has a relatively
large flank angle of about 60.degree. and a relatively small pitch
of 1.6 mm, for example. The metallic clip has a through-bore which
traverses either clip bow. One clip bow has formed in it a thread.
The metallic clip is slid onto the edge of a carrier material so
that its through-bore is aligned with a through-bore of the carrier
material. The metallic screw is then rotated into the flush
through-bores with its thread interacting with the thread of the
metallic clip until the metallic screw is secured in place with the
metallic clip and the carrier structural component which is
received thereby. The structural component is secured on a
through-bore between the screw head and the metallic clip. The
threaded joint is self-locking.
[0005] Fastenings of this type are also employed specifically in
automobile manufacture when structural components require to be
attached in the marginal area of metal sheetings, e.g. panelings to
wheel housings or safety bumpers to the body.
[0006] A drawback is that, apart from the plastic plug and the
metallic clip, different screws need to be manufactured, kept in
stock, and handled for these different fastenings which are
employed in the same areas.
[0007] Based on this fact, it is an object of the invention to
provide a less expensive fastening system for fixing structural
components to carrier materials.
[0008] The object is attained by a fastening system having the
features of claim 1. Advantageous aspects of the fastening system
are given in the sub-claims.
[0009] The inventive fastening system includes
[0010] a screw which comprises a screw head and on a screw shank a
thread which with respect to the pitch and the flank angle is
matched to the formation of a thread in a bore of a plastic
material, and at least one axially extending deepening on the
thread root, and
[0011] a plastic material with a bore into which the screw may be
threaded whilst forming a thread and/or
[0012] a clip with two clip bows and a clip back which connects
these and which comprises a through-bore traversing the clip bows,
with a thread for rotating in the screw and at least one resilient
lug aligned radially to the axis of the through-bore for latching
into the at least one deepening of the screw when this is rotated
into the through-bore of the clip.
[0013] The fastening system comprises a "plastic-tailored" screw.
This means that the screw is configured as to its pitch and flank
angle in such a way that it is capable of forming an appropriate
thread in a bore of a plastic material. At this point, the pitch
must not be dimensioned so small and the flank angle must not be
dimensioned so large that the formation of a thread in the bore can
no longer be achieved at an acceptable expenditure and the
load-carrying ability of the threaded joint is too low. On the
other hand, the pitch must not be chosen so large to prevent the
engaging threads from being self-locking and the flank angle chosen
must not be chosen so small that the load-carrying ability of the
thread flank becomes insufficient.
[0014] Preferably, the thread of the screw has a flank angle of
about 20 to 40.degree., especially about 30.degree.. Preferably,
the thread of the screw further has a pitch of from 1.5 to 3.5 mm,
specifically 2.2 mm (cf. the embodiment), which particularly
depends on the measure of the outside diameter.
[0015] However, the ranges given may be exceeded or remain below
the mark because shaping a plastic-tailored thread may be dependent
on influencing parameters such as the surface finish of the screw
and the substance of the plastic material, the dimensions of the
screw and the bore, and the speed of the screw-driver for rotating
in the screw, which may vary very much from one case to
another.
[0016] The design of the screw ensures that structural components
can be fixed to plastic materials. This may concern, in particular,
a plug made of plastic or carrier materials in plastic or plastic
portions of carrier materials thereof. In particular, it may
concern a plastic dome of a carrier material which may be of a
different material. The carrier materials may be both thick and
flat.
[0017] Furthermore, it is possible to fix a structural component to
a flat carrier material or a flat portion of a carrier material by
means of a clip. It has a thread which is matched to the thread of
the plastic-tailored screw, i.e. it has a pitch larger than that of
a conventional metallic clip. This screwed joint has less
self-locking properties. However, it is ensured that the clip be
locked by the fact that the clip latches its at least one resilient
lug into the at least one axially extending deepening of the screw
when this one has been rotated into the clip. It is understood here
that the at least one lug may be latched several times into the at
least one deepening while the screw is rotated in, and may be
unlatched again therefrom. Preferably, there are several deepenings
to make arresting possible in various angular positions of the
screw. Also, several lugs may be uniformly spaced around the
through-bore of the clip in order to uniformly load the screw at
the circumference.
[0018] The deepening extends in the axial direction of the screw,
which deepening may also run in a helical shape. What is essential
is that it has a pitch which at least differs from that of the
screw thread. Preferably, however, the at least one deepening
extends parallel to the screw shank. Since the screw thread has a
relatively large pitch it may have a thread root which may be
relatively wide and on which at least one deepening may be
accommodated.
[0019] The at least one deepening may be of a symmetrical (e.g. a U
or V-shaped) or an asymmetrical (e.g. a saw-tooth shaped)
cross-section. The latter offers a possibility, while the screw is
rotated into the thread of the clip, to make it easier for the lug
to exit from the deepening by appropriately inclining one flank
thereof and, if there is a load in the opposed direction, to make
it more difficult for the lug to exit from the deepening by causing
the lug to abut against a correspondingly steep flank.
[0020] The clip preferably is designed as a spring clip where a
spring bow may have an angled tab to make it easier to slide the
spring clip onto a flat material. In addition, the clip may have
one or more barbs at the inside to secure the clip to a structural
component in a pre-assembled position.
[0021] The at least one lug may have an end portion tapering
towards the free end, which makes it more convenient to rotate in
the screw and to precisely lock it in a determined position.
Preferably, the at least one lug is bent out of the flat material
of the clip. Although the material of the clip may be a metal,
particularly a metal sheeting, a plastic may be considered as
well.
[0022] The invention will now be explained with reference to the
accompanying drawings of an embodiment. In the drawings,
[0023] FIGS. 1a to d show a plastic-tailored screw in a lateral
view (FIG. 1a), a top view (FIG. 1b), a section taken along lines
c-c of FIG. 1a (FIG. 1c), and an enlarged view of the detail d of
FIG. 1c (FIG. 1d);
[0024] FIGS. 2a to d show a plug in plastic material in a lateral
view (FIG. 2a), a top view (FIG. 2b), a section taken along lines
c-c of FIG. 2b (FIG. 2c), and a section taken along lines d-d of
FIG. 2c (FIG. 2d);
[0025] FIGS. 3a to c show a clip in a top view (FIG. 3a), a
longitudinal section (FIG. 3b), and a perspective view oblique from
top with an inserted screw of FIG. 1 (FIG. 3c);
[0026] FIG. 4 shows the lug of the clip engaging a deepening of the
screw in a strongly enlarged partial section.
[0027] Referring to FIG. 1, a screw 1 has a screw head 2 formed as
a mushroom-head with a flange at its underside, and a screw shank
3. The screw shank 3 carries a thread (4) which is designed as a
V-cut thread. The V-cut thread 4 is gradually flattened towards the
obtuse end of the screw shank 3.
[0028] The thread 4 has a pitch h of about 2.2 mm and a flank angle
.alpha. of 30.degree.. In the embodiment, the outer diameter d of
the thread 4 is about 5.18 mm and its minor diameter d.sub.1 is
about 3.1 mm.
[0029] Disposed on the screw shank 3 at the cylindrical thread root
are seven groove-shaped deepenings 5 uniformly distributed over its
circumference which extend in the axial direction of the screw
shank 3. The deepenings 5 are interrupted by the flanks of the
thread 4. The deepenings 5 are of a substantially V-shaped
cross-section having an angle of aperture of 80.degree., for
example. The deepenings are radiused at their root and their
transition zone to the outer circumference of the screw shank
3.
[0030] The screw head 2 has a tool catch accessible from the top
which is designed as an inside hexagon circular socket or inside
star recess (Torx.RTM.--applicant's registered mark), but can also
be a hexagon socket or intersecting slots.
[0031] Within the scope of the invention, the screw 1 may be
subjected to various hardening processes, i.e. it may be
heat-treated or case-hardened. Other head shapes, thread profiles,
and thread crests are incorporated as well. In particular,
symmetrical thread profiles are taken into consideration.
[0032] Referring to FIG. 2, a plug 7 in plastic material is shown.
It has a plug body 8 which is adapted to be inserted into the
through-bore of a flat carrier material and has a bore 9 oriented
in the direction of insertion for fastening the screw 1. At top,
the plug body 8 carries a resilient sealing collar 10 which extends
outwardly around the plug body 8 radially to the direction of
insertion and has an annular sealing surface 11 which is oriented
in the direction of insertion. The sealing collar 10 is made of a
material softer than that of the plug body 8. In the embodiment,
the sealing collar 10 is fixed to the plug body 8 by chemical
adhesion.
[0033] The plug body 8 has barbs 12, 13 disposed at its outer
circumference which let pass in the direction of insertion and
block in the direction opposed to insertion. At this point, the
barb 12 is designed as a detent foot which will be compressed
during the forcing-in operation. The barb 13 is a hinged foot which
can back out inwardly into a groove 14.
[0034] The plug body 8 tapers towards the lower end. In the
embodiment, the tapering is conical at an angle of 60.degree.. This
facilitates insertion into the through-bore of the carrier
material.
[0035] At bottom, the plug body 8 has a tip 15 which includes
strength-reducing lines 16. This makes it possible, by breaking the
tip open, to rotate in a screw which cannot be fully received by
the bore 9.
[0036] The plug 7 is inserted in a through-bore of a flat material
until one of the barbs 12, 13 snaps below the underside of the flat
material. The sealing collar 10 will then sealingly abut against
the upper surface of the flat material which, for example, may be
the metal sheeting of an automobile body. Subsequently, the screw 1
may be rotated into the bore 9, thus forming a thread in the bore
9. The large pitch and the relatively acute flank angle of the
thread 4 of the screw 1 make it more convenient to rotate in a
thread of high load-carrying ability. At this point, a structural
component to be fastened is guided on the screw on a bore so that
the structural component ultimately comes to be sandwiched between
the screw head 2 and the plug 7 or the upper surface of the flat
material. This threaded joint is self-locking.
[0037] FIG. 3 shows a clip 17 which is made of a metal sheeting. It
has two clip bows 18, 19 which are laterally interconnected via a
clip back 20. The clip bow 19 is inclined at an acute angle to the
clip bow 18 and defines a spring bow. It has an angled tab 21 at
its end which makes it easier to slide it onto the edge of a flat
material. The tab 21 is joined to the clip bow 19 only in the
central region so that it has pointed portions at either side which
extend below the clip bow 19 and define barbs 22', 22". These barbs
22', 22" help in securing the clip 17 in a pre-assembled position
by digging their way into the upper surface of the flat carrier
material which, for example, may be of plastic or metal.
[0038] The clip bows 18, 19 are traversed by a through-bore 23',
23" approximately in their centre. The portion 23" of the
through-bore has a upwardly facing or bordered-up edge 23"'. Formed
in the inside of this edge 23"' is a thread 24 which is dimensioned
so as to be able to interact with the thread 4 of the screw 1. The
thread 24 extends only approximately over a complete thread
turn.
[0039] Clips which are meant for a larger range of clipping widths
may also have a bow portion separated from the clip bow 19 at three
sides, which is bent out of the clip bow 19 so as to extend
approximately parallel to the clip bow 18 and which houses the
portion 23" of the through-bore. This allows to improve the
alignment of the portions 23', 23" on each other.
[0040] Finally, the clip 17 has a lug 25 which also is bent out of
the sheeting. To this end, the lug 25 is separated (e.g. punched
out) from the marginal areas of the clip bows 18, 19 and the clip
back 20 and is merely joined to the clip bow 19. It is bent back
over the clip bow 19 so as to extend its end portion 26 tapering
towards its free end beyond the marginal area of the through-bore
23', 23". At this point, the end portion 26 is aligned
approximately radially to the through-bore 23', 23".
[0041] For purposes of fastening, a clip 17 is slid onto the
marginal area of a metal sheeting or plastic part and is flushly
placed, with its through-bore 23', 23", above a through-bore
thereof. The barbs 22', 22" hold the clip 17 in place in this
pre-assembled position.
[0042] Subsequently, a screw 1 is rotated into the through-bore
23', 23", namely starting from the side of the clip bow 18. The
screw thread 4 grips behind the thread 24 of the clip 17 here.
While the screw 1 is being rotated in the lug 25 will snap into
each continuous deepening 5 of the screw shank 3 (cf. FIG. 4).
Finally, a structural component slipped onto the screw shank 3 is
secured in place between the screw head 2 and the clip bow 18 or
the carrier material. At the same time, the clip bow 19 is secured
in place to the inside of the carrier material. After it is
sufficiently secured in place the screw 1 is brought into a
rotational position in which the lug 25 latches into a deepening 5.
After this, the fastening is self-locking although the acute angle
.alpha. and the large thread pitch h, while interacting with the
thread 24 of the clip alone would not cause a sufficient
self-locking action.
[0043] What can be reached by arranging several lugs 25 at angular
spacings which deviate from those of the deepenings 5 is that a lug
25 engages a deepening 5 virtually in any angular position of the
screw. This is possible, for example, if the lugs are arranged in
differing angular spacings over the circumference and/or if there
are differing numbers of lugs and deepenings.
[0044] Thus, the fastening system which only has a screw 1 makes it
possible to provide self-locking fastenings, especially on flat
materials, by resorting to a plug 10 or a clamp 17 if this is
necessary.
* * * * *