U.S. patent number 3,921,979 [Application Number 05/420,520] was granted by the patent office on 1975-11-25 for intermediate members for the crossing points of tennis racket stringings.
This patent grant is currently assigned to Babolat-Maillot-Witt. Invention is credited to Gebhard Dischinger.
United States Patent |
3,921,979 |
Dischinger |
November 25, 1975 |
Intermediate members for the crossing points of tennis racket
stringings
Abstract
Intermediate members for the crossing points of tennis racket
stringings in which the intermediate members are formed as
crosspiece guides having crossing tubular or, respectively,
groove-shaped portions, which at least partly encompass the strings
by means of suitable wings, and which are constituted of a
relatively low-friction, self-lubricating plastic or synthetic
material.
Inventors: |
Dischinger; Gebhard (Bremen,
DT) |
Assignee: |
Babolat-Maillot-Witt (Lyon,
FR)
|
Family
ID: |
5863250 |
Appl.
No.: |
05/420,520 |
Filed: |
November 30, 1973 |
Foreign Application Priority Data
Current U.S.
Class: |
473/543; D21/729;
273/DIG.4 |
Current CPC
Class: |
A63B
51/11 (20151001); Y10S 273/04 (20130101) |
Current International
Class: |
A63B
51/00 (20060101); A63B 51/10 (20060101); A63B
051/00 () |
Field of
Search: |
;273/73R,73D,DIG.4,DIG.12,DIG.29,68 ;124/3A,41A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
24,856 |
|
Nov 1913 |
|
UK |
|
1,398,833 |
|
Apr 1965 |
|
FR |
|
640,448 |
|
Mar 1928 |
|
FR |
|
786,619 |
|
Jun 1935 |
|
FR |
|
Other References
Dupont Information Bulletin: "Teflon 100 FEP;" June 1960, pp. 1-3.
.
Archery Magazine, Vol. 34, Aug. 1962, p. 35..
|
Primary Examiner: Apley; Richard J.
Attorney, Agent or Firm: Haseltine, Lake & Waters
Claims
What is claimed is:
1. An intermediate crosspiece guide member formed of a low-friction
self-lubricating synthetic material for use in a tennis racket
stringing having crossing gutstrings, said member adapted to be
mounted intermediate the gutstrings at the crossings thereof, said
member comprising first and second recessed portions on opposite
sides thereof, said recessed portions each including groove-forming
pairs of upstanding wings adapted to extend along and engage at
least part of the outer surface of gutstrings adapted to be
received in said recessed portions, the groove-forming wings of
said first recessed portion extending in a parallel spaced plane
and transversely of the groove-forming wings of said second
recessed portion adapted to prevent contact between adjacent
gutstrings at the crossing thereof and to concurrently guide said
gutstrings in coplanar and transverse directions.
2. An improvement as claimed in claim 1, said synthetic material
being polyformaldehyde.
3. An improvement as claimed in claim 1, said synthetic material
being polytetrafluoroethylene.
4. An improvement as claimed in claim 1, said synthetic material
being constituted of a polypropylene base and a molybdenum
additive.
5. An improvement as claimed in claim 1, said synthetic material
being constituted of a polypropylene base and a graphite
additive.
6. An improvement as claimed in claim 1, said synthetic material
being constituted of a polyamide base and a molybdenum
additive.
7. An improvement as claimed in claim 1, said synthetic material
being constituted of a polyamide base and a graphite additive.
8. An improvement as claimed in claim 1, each wing of said pair of
upstanding wings being arcuately bent towards the other wing of
said pair so as to form a substantially tubular configuration
having a slot between the adjacent free ends of said wings.
9. An improvement as claimed in claim 8, said wings being
elastically deformable.
10. An improvement as claimed in claim 1, each said pair of wings
comprising symmetrical mirror-image shaped wings.
11. An improvement as claimed in claim 1, comprising reinforcing
flange means connected to said groove-forming wings.
12. An improvement as claimed in claim 1, said wings each having
profiled end portions.
13. An improvement as claimed in claim 1, said upstanding wings
being curved so as to form a generally hemisphericallyshaped groove
therebetween.
14. An improvement as claimed in claim 1, said upstanding wings of
each pair having generally parallel wall portions.
Description
FIELD OF THE INVENTION
The present invention relates to intermediate members for the
string cross points of tennis racket stringings, and with the
intermediate members including recess on both sides thereof adapted
to receive the mutually crossed strings.
DISCUSSION OF THE PRIOR ART
Presently known tennis racket stringings with gutstrings, which
evidence, in comparison with synthetic material strings, a superior
enhanced degree of elasticity and, consequently, an improved
playing relationship, are however subject to the important
disadvantage in that the life expectancy thereof, particularly in
view of mechanical wear at the cross-over points between two
strings, in contrast with synthetic strings, is relatively short.
In order to avoid this disadvantage various known intermediate
members are used, for example, in the shape of discs or plates
formed of leather or the like, having recesses on both sides
thereof adapted to receive the mutually crossing strings. These
intermediate members are relatively stiff and are intended to form,
by means of an increase in the coefficient of friction at the
cross-over points, and intimate connection while preventing mutual
displacement of the strings. However, in that case there is
obtained, at the expense of the positive properties of gutstrings,
a racket stringing having overall relatively poor elasticity
characteristics and deficient playing properties, and which due to
an unfavorable load distribution and unavoidable friction is
readily damaged under impact loads.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide
intermediate members for the string crossing points of tennis
racket stringings which, without adversely affecting the degree of
elasticity and resilience of the tennis racket stringings, will in
an effective manner prevent the rapid destruction of the tennis
racket strings.
The implementation of the object of the present invention is
achieved in that the intermediate members are formed as crosspiece
guides having crossing tubular or, respectively, grooveshaped
portions, which at least partly encompass the strings by means of
suitable wings, and which are constituted of a relatively
low-friction, self-lubricating plastic or synthetic material.
The inventive tennis racket stringing utilizes the collective
advantages of the gutstrings, namely in particular, their
outstanding elastic characteristics to the fullest extent, while
concurrently preventing damage by a considerable reduction in the
friction at the crossing points through the satisfactory guidance
of the individual strings. From the foregoing there is achieved an
outstanding elastic playing characteristic with a good traction
capacity of the upper surface of the tennis racket stringing and
thereby a better, and for the same load requirement, accelerated
ball conveyance.
Although the inventive intermediate members or crosspiece guides
are, above all, particularly suited for tennis racket stringings
employing gutstrings, they may also be advantageously employed in
connection with plastic or synthetic material strings so as to
improve either the elasticity and/or the contact properties of the
stringing, as well as playing characteristics of the tennis
racket.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is now described in detail with respect to various
embodiments of the tennis racket stringing, having reference to the
accompanying drawings, in which:
FIG. 1 illustrates a perspective, partly sectioned and enlarged
fragmentary view of a typical tennis racket stringing showing the
impact load thereon during impact by a tennis ball;
FIG. 2 is a schematic representation of sequential wear or
chafing-through conditions of two crossed-over strings;
FIG. 3 shows a perspective representation of a crossing point
provided with a crosspiece guide formed in accordance with a first
embodiment of the invention;
FIG. 3a is a sectional view similar to FIG. 3 showing a crosspiece
guide constructed according to a second embodiment;
FIG. 4 is a sectional view similar to FIG. 3 showing a crosspiece
guide constructed according to a third embodiment;
FIG. 5 is a plan view of a portion of a tennis racket stringing
having mounted thereon crosspiece guides constructed according to
the embodiment of FIG. 3;
FIG. 6 is a sectional view taken along line VI--VI in FIG. 5;
FIG. 7 is a side elevational view of a fourth embodiment of a
crosspiece guide constructed according to the invention;
FIG. 7a is a bottom plan view of the crosspiece guide of FIG.
7;
FIG. 8 is a side elevational view similar to FIG. 7 of a slightly
modified fifth embodiment of a crosspiece guide according to the
invention;
FIG. 8a is a bottom plan view of the crosspiece guide of FIG.
8;
FIG. 9 is a plan view of a portion of a tennis racket stringing
having mounted thereon crosspiece guides constructed according to
the embodiment of FIGS. 7 and 7a; and
FIG. 10 is a sectional view taken along line X--X in FIG. 9.
DETAILED DESCRIPTION
Referring now in greater particularity to the drawings, FIG. 1
illustrates in a fragmentary enlarged view, partly in section, a
standard type of tennis racket stringing showing the deformation of
the strings in the direction of arrow 10 upon impact by an oncoming
tennis ball. Represented are a plurality of parallel, radially
sectioned strings 14, and a string 16 extending perpendicularly
thereto, and which is twisted through the strings 14 strings 16, as
shown in FIG. 1. The impact of the tennis ball 12 deforms the
strings at the impact point approximately into the configuration
schematically illustrated by string 16, in which the impulse of the
tennis ball in the direction of the arrow 18 is transmitted to the
strings, as is illustrated by the intermediate string 20. By means
of this impulse, each string which is positioned above at the
crossing point is compressed against the there-below positioned
string (in the illustrated example against the string 16).
Consequently, the approximately point-shaped contact surface
between two crossing-over strings is widened into a larger contact
surface having, for example, a width x. Through the string which is
located beneath each crossing point, for example, string 16, there
is generated a reaction force extending in the direction of arrow
22. There is formed, concurrently an increase in the friction
surface and an increase in the contact pressure, resulting in an
extremely large frictional resistance between the two strings. Due
to the elasticity of the individual strings, upon the
back-and-forth movement of the stringing surface, and in particular
during rebounding, which occasionally does not occur in a direction
perpendicular relative to the stringing surface, an at least
partially mutual string displacement becomes unavoidable. The
thereby generated through-chafing or wear conditions are
illustrated in FIG. 2 in four different stages thereof. Individual
strings 14a, 14b, 14c and 14d which extend perpendicular to a
transversely positioned string 16, and which are positioned
therebelow at the crossing points 26a, 26b, 26c and 26d, evidence a
widely divergent advancing wear appearances. Extending from the
string 14a which characterizes the new condition of the tennis
racket stringing, there are illustrated the sequentially increasing
wear conditions of the contact surfaces 26b, 26c and 26d. The
frictional wear finally leads to the condition in which one of the
strings, upon impact by the tennis ball, fails to resist the load
and consequently tears.
The various embodiments of FIGS. 3, 3a and 4 illustrate crosspiece
guides 28, which are introduced between two crossing-over strings
16 and 20.
Referring to FIG. 3, showing a first embodiment of the invention,
illustrated at least partly in section, this crosspiece guide
comprises two perpendicularly extending tubularly or trough-shaped
members 30, 32 which, by means of two symmetrical mirror-image
shaped wings or side walls 34 and 36, encompass the strings 16 and
20 for about one-half their circumferences, and which then extend
substantially parallel to each and tangential relative to the
respective strings beyond the latter. This construction forms
essentially groove-like depressions, in which the strings 16, 20
extend in side wall-contact with the contact wings 34, 36. This
first embodiment is of particularly simple construction, and
facilitates the rapid and uncomplicated insertion of the individual
strings into the crosspiece guides.
The second embodiment illustrated in FIG. 3a of the drawing
generally corresponds with that of FIG. 3, however, in this
modification the tubular-like portions 30, 32 only extend so as to
encompass the strings 16, 20 for only approximately one-half the
circumferences thereof. Inasmuch as the strings 16, 20 are under
axial tension, a crosspiece guide 28 of the type described is in
itself adequate to obtain an adequate guide and securing of the
various strings 16, 20 in the region of the cross over points. In
this embodiment it is also possible to effect the insertion of the
strings 16, 20 into the respective curved recesses without the need
for additional measures. Depending upon the occasion, the wings of
the tubular-like members 30, 32 may be, according to any particular
requirement, either shortened or lengthened.
In FIG. 4 there is illustrated a third embodiment of a crosspiece
guide 28 in which the tubular-like members 30, 32 almost entirely
encompass the strings 16, 20. The respective wing portions, as in
the other embodiments, are symmetrically mirror-image shaped
relative to each other, and their free ends bend into proximity to
each other at the upper surface of each of the strings 16, 20. In
order to facilitate the subsequent application or replacement of
the crosspiece guides 28 according to the embodiment, the wing
portions of the tubular-like members 30, 32 are preferably
elastically constructed so that the strings 16, 20, after bending
open of the wings, are clampingly encompassed by the latter upon
snapping shut of the wings.
While the embodiments of FIGS. 3 and 4 are in particular also
adapted to prevent any direct impact contact by the oncoming tennis
balls, which provides for a considerable reduction in mechanical
wear, the embodiment of FIG. 3a is particularly simple in
construction and in material savings. However, in common in all
embodiments, due to the lack of friction in the region of the
cross-over points, the various strings 16, 20 may be displaced
relative to each other in an unhindered manner in response to any
load or rotation imparted thereto.
In FIG. 5 there is illustrated a portion of a tennis racket
stringing in which there are positioned crosspiece guides 28
constructed according to FIG. 3 at the cross-over points of the
crossing strings 14, 16. From FIG. 6, which shows a sectional view
of the stringing of FIG. 5 taken along line VI--VI, there may be
clearly ascertained the inter-weaving of the individual strings 14
and 16. The tubular-like members 30, 32, whose wings 34, 36 extend
up to or beyond the outer sides of the strings 16, 20, thereby
prevent the direct contact between the ball and the strings in at
least in the region of the cross-over points.
From FIGS. 7 and 7a there is ascertained in, respectively, side and
plan views, a fourth embodiment of crosspiece guide 37. This
crosspiece guide structure includes relatively perpendicularly
extending tubular-like members 38 and 40, which closely adhere to
the string at the cross-over point and which are mutually
reinforced through flanges 42. The tubular-like members 38 and 40
are, in the longitudinal direction of the recesses or bores 44
which are adapted to receive the strings, provided with a slot 46,
by means of which they may elastically be bent apart so as to
facilitate insertion of the string into the recess 44.
Subsequently, the tubular-like member snaps closed and thereby
fixedly retains the string in that position.
A fifth embodiment which largely corresponds with the fourth
embodiment illustrated in FIGS. 7, 7a, is ascertained from FIGS. 8
and 8a. The crosspiece guide crossing elements 37a shown therein
comprises, in lieu of the tubular-like members, two mutually
perpendicularly extending ridge-like members 38a, 40a which, in a
manner similar to that of the embodiment of FIG. 3, serve as guide
grooves for the strings (not shown). The outwardly projecting wings
of the rigde-like members 38a and 40a may be formed as high as
required, and also different with respect to each other.
Additionally, flanges 42a which interconnect the ridge-like members
38a, 40a serve as reinforcements therefore. The crosspiece guides
37a of this embodiment are somewhat simpler in construction than
the crosspiece guides 37 of the fourth embodiment, since the
ridge-like members 38a, 40a do not include ring-like closed and
consequently elastically formed regions.
A section of a tennis racket stringing having crosspiece guides 37a
of the type shown in FIGS. 7, 7a may be ascertained from FIG. 9 of
the drawings. Therein it is clearly noticeable, that the
tubular-like closed, and with suitable longitudinal slots provided
portions 38, 40, encompass perpendicular to each other extending
strings 14, 16, so as to guide and protect these in the regions of
their cross-over points. These slots 46 extend in longitudinal
directions in conformance with the respective strings 14, 16.
In FIG. 10 there is shown a sectional view taken along line X--X in
FIG. 9, and from which there may be ascertained the sinuous
interweaving of the individual strings 14, 16. Further, therein is
illustrated the manner in which the tubular-like members 38, 40
adhere against the strings.
Furthermore, it is advantageous that the wings 34, 36 and/or the
ridge-like members 38a, 40a be profiled at the ends thereof for
enhancing their gripping ability. Thereby, as indicated it becomes
still simpler to impart a spin to the tennis ball during play and
to improvedly guide the latter.
In order to have no frictional forces generated between the
gutstrings 14, 16, 20 and the individual crosspiece guides 28, 37
and 37a, and thereby at all cross-over points for any two strings,
it is preferable that the low-friction, self-lubricating synthetic
or plastic material for the crosspiece guides be constituted of
polyformaldehyde or polytetrafluoroethylene (Teflon). In lieu
thereof it is also possible that the plastic material be
constituted of a polypropylene or polyamide base with a molybdenum
or graphite additive. These materials provide a practically
negligible degree of friction even at higher forces caused by the
axial tensioning of the strings.
Due to the almost frictionless mutual sliding of the strings within
the crosspiece guides, the elasticity of the novel gutstring
stringing is considerably increased above the elasticity for prior
art tennis racket stringings. Independently of the advantage that
the play with this type of tennis racket is considerably more
comfortable and feel-sensitive, the player receives a considerably
improved playing advantage due to the higher level of employment of
the maximum elasticity characteristics of the gutstrings since, for
example, by applying the same degree of force, the play is
considerably accelerated. The crosspiece guides in the regions of
the cross-over points provide a good support for the individual
strings and a satisfactory guide while concurrently preventing
friction which would tend to cause damage, and allow for the
sliding-through movement of the individual strings so as to render
possible the unhindered use of their elastic characteristics.
In particular, the crosspiece guides employed in the stringing
allow for the use of thinner gutstrings, which additionally
enhances the elasticity, and reduces the cost of the tennis racket
stringing.
While there has been shown what is considered to be the preferred
embodiment of the invention, it will be obvious that modifications
may be made which come within the scope of the disclosure of the
specification.
* * * * *