Note: Descriptions are shown in the official language in which they were submitted.
133~130
HIGH DENSITY FILAMENT
WINDING AND METHOD FOR PRODUCING
IMPROVED CROSSOVERS AND INSIDE PAYOUT
BACKGROUND OF THE INVENTION
5 1. Field of the Invention
The present invention relates generally to winding
filaments, and, more particularly, to a winding of high
packing density and a method of making.
2. Description of Related Art
There are situations in which it is desirable to be
able to pay out a metal wire or optical fiber of
considerable length for use as a data link. For example,
many present day weapon systems include a launched
missile with a wire or fiber optic data link wound on a
bobbin or spool which pays out at a very high rate of
speed during use.
Several criteria must be met in order to provide a
satisfactory winding which can act as a missile data
link. First of all, payout must be accomplished with a
minimum of tension on the filament to prevent breakage,
or in the case of an optical fiber even to prevent
microbending which reduces signal transmission.
Secondly, the winding should be stable so as to permit
storage without collapsing from its wound configuration.
Lastly, the winding
~
1333130
1 should be dense and compact so as to take as little space
as necessary.
Certain present day high speed filament dispensers
have the filament in one layer nest between turns of
adjacent layers. To maintain this condition, in certain
known dispensers each layer is stepped back several turns
from the underlying layer. This results in tapered ends
for the winding which reduces volumetric efficiency.
A disadvantage especially found in cylindrical
layered windings is the frictional drag on payout result-
ing from an outer layer being removed from an underlying
layer. One way of reducing this problem is to provide a
winding having an inside-out payout which not only pro-
vides exceptional volumetric efficiency but allows the
winding to be stored without being subjected to undesir-
ably high levels of tensile stress. This latter point is
important especially for optical fiber cables which are
subject to static fatigue and optical signal attenuation
due to loads imposed by winding.
Known inside payout dispensers employ a "basket
weave" winding technique which results in a substantial
amount of empty space reducing volumetric efficiency.
Moreover, the relatively large effective pitch of such a
winding causes a-correspondingly large modulation in
instantaneous payout velocity reducing achievable vehicle
speed for a given filament strength.
It is also desirable for windings, especially
inside payout windings, to have squared ends. However,
closely packed windings with squared ends are not easily
wound, and in the past were not obtainable by high speed,
automatic techniques.
The foregoing problems have been exacerbated by
the problem of crossovers, Crossovers heretofore have
generally advanced a full pitch at each crossover region
of a winding turn and/or have resulted in windings with
133~130
1 irregular (i.e., non-squared) ends. See in this connec-
tion, Winding Long Slender Coils ~y The Orthocyclic Method
by Halder W. C. Aamot, Special Report 128, U.S. Army
Materiel Co~mAn~, February 1969. Such uncontrolled cross-
overs have required frequent manual "massage" to m;n;mizewinding disturbances, bulges, and other irregularities
which may prevent successful winding and payout, and
reduce volumetric efficiency.
SUMMARY OF THE I~v~lION
There is provided in accordance with the present
invention a filament winding (e.g., wire, optical fiber)
in which each layer has a plurality of turns nested
between turns of the underlying layer, each turn crossing
over underlying turns in at least two regions. Each
crossing filament turn has an advance in a crossing
region which substantially aligns with a crossover region
in the underlying layer. The winding so produc-ed enables
achieving a winding having squared ends and enhanced
volumetric efficiency.
These windings can be made by high-speed, auto-
matic machine techniques. One especially advantageous
use of windings described here made in the inside payout
form, is to provide a data link from a launched missile
to its launch site.
The winding method of the invention includes
laying down a base wire layer on a mandrel over which a
guide layer is formed, the guide layer turns being nested
in the wire layer and spaced apart. The filament winding
is formed by nesting in the interturn spaces of the guide
layer.
An adhesive binder is applied to the filament as
it is wound. After cure of the binder several sacrifi-
cial filament layers, which are laid down on the guide
wire before the actual filament, are removed allowing the
winding to be removed from the mandrel. In this manner,
133~130
the baselayer can remain on the mandrel and may be used
again.
The guide wire layer may be laid down by a bifilar
technique in which two wires of differing diameters
(e.g., 6 and 3 mils over a 5 mil wire base) are wound
side-by-side and the larger wire removed leaving the
desired gap to receive the filament.
Another aspect of this invention is as follows:
A method of forming a densely packed winding from a
filament of given diameter, comprising the steps of:
providing a mandrel with a radially extending
flange;
wrapping a base wire on the mandrel to form a first
layer;
wrapping a second layer over the first layer using
first and second guide wires in side-by-side relation;
removing the second guide wire leaving a space
between adjacent turns of the first guide wire; and
wrapping a first layer of the filament nesting in
the spaces between the first guide wire turns, and
subsequent layers formed by reversing the direction of
wrapping over the underlying layer, an outermost turn of
each layer contacting the flange.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. lA is a perspective view of a prior art
winding, and FIG. lB is a stylized illustration of
uncontrolled crossovers appearing in prior art windings.
1333130
5a
FIG. 2A is a perspective view of an inside payout
filament winding; FIGS. 2B and 2C are a stylized
depiction of a winding of the invention having improved
crossovers and sectional view thereof; FIG. 2D is a
stylized depiction of an alternative winding geometry.
FIG. 3 is a side elevational view of a mandrel and
winding of the present invention.
FIG. 4 is a side elevational view of a mandrel with
removable flanges.
FIGS. 5A and 5B are pictorial views of windings in
accordance with the present invention.
FIGS. 6A and 6B are pictorial views showing windings
with sacrificial layers removed.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, "pitch" means the axial advance of
the winding associated with one turn.
As used herein, the term "filament" means optical
fiber, but may also include more generally, wires,
fibers, tubes, hoses and other items to be wound.
Turning now to the drawings and particularly FIG.
lA, a filament dispenser 10 of the prior art is shown
having tapered construction in order to reduce drag on
the filament 12 as it is removed from one end. A first
l33~l~o
1 deficiency is that the tapered construction is not
volumetrically efficient. Also, since alternative
layers are oppositely wound, there is the matter of
maintAi n; ng regular cross-over geometry in order to
achieve a precision filament winding. Dashed lines 14
define the area within which the crossovers typically
occur on a winding spool.
Alternate winding layers have been wound as right-
hand and lefthand helixes, which results in a filament
crossing over an underlying filament twice each turn.
In the past, precision filament winding was only achieved
by interrupting winding to manually adjust (massage)
crossovers or risk winding disturbances that result from
uncontrolled crossover patterns. A typical crossover
pattern obtained heretofore is shown in FIG. lB. Not
only can improper crossovers (e.g., stacked in one or a
few positions) interfere with winding, they can also
prevent formation of squared ends which are desirable for
inside payout applications.
Reference is now made to FIGS. 2A-2C depicting
filament windings according to this invention. FIG. 2A
shows an inside payout winding 16 with two crossover
regions 18 and 20 and having squared ends 22 and 24. The
wind ing has an overall cylindrical shape and the filament
26 pulls off from the coil interior in what is termed
inside payout. It is seen that the crossover region
rotates or precesses about the winding which distributes
poten~ial crossover buildups in the crossover regions.
FIGS. 2B and 2C show the improved crossover
arrangement in more detail and particularly as they occur
in closely packed and deep nested versions, respectively.
FIG. 4 depicts a winding form 28 especially
advantageous in practicing this invention including a
generally cylindrical mandrel 30 with two removable
flanges 32 and 34 secured onto the two ends of the mandrel
133~ 1 30
1 in a manner that permits axial position and tilt to be
precisely adjusted to the required position relative to
the pattern on the mandrel. Each flange has a flat face
36 which extends radially away from the mandrel circum-
ferential surface. The winding space 38 defined by the
circumferential mandrel surface and the two flange faces
36 will be either rectangular or square in cross-section
dep~n~; ng upon the axial spacing of the flanges along the
mandrel. A filament winding developed in space 38 and
which squares off against faces 36 will possess the
optimum volumetric efficiency, all other things equal.
For the ensuing details of a first embodiment of
this invention reference is now made to FIG. 3. The
mandrel 30 is seen to specifically include a first or
major circumferential surface 40 of a first diameter, a
second circumferential surface 42 of a second diameter
greater than the first, the latter surface being located
- adjacent a mandrel end and extending for only a relatively
short axial distance. A conical wall 44 joins the sur-
faces 40 and 42, the angle of juncture with 42 exceeding
90 degrees. It is assumed that a winding is to be
made from an optical fiber 46. Before beginning the
optical fiber winding and before locating the flanges 32
and 34 in place on the mandrel, one layer of a base wire
48 is helically wound onto the mandrel surface 40, sub-
stantially covering the surface with the last turn 50
raised slightly onto the conical wall or lip 44 which
wedges the base wire layer firmly in place. This wedging
is always below or underneath the subsequently wound
guide layer and, therefore, does not interfere with the
flanges. The base wire on completion of turn 50 con-
tinues to be wound back onto the base layer forming a
guide layer 52 in which adjacent turns nest with the base
layer so as to be spaced apart one wire width. The base
wire ends are secured by conventional anchor, for
8 1333130
1 example, (not shown) fixedly locating the base and guide
layers to the mandrel. The flanges extend over the first
few turns of the base and guide layers at each end which
may produce some irregularity at the ends in the final
winding. A slight space 54 exists between the flanges
inner surface and the outermost part of the guide layer
permitting ready mounting and removal of the flange
without disturbing either the guide or base layers.
On the opposite side of the mandrel, the guide
wires of layer 52 are displaced by one base wire diameter
because of the half-pitch advance steps. This results in
a half-winding pitch gap between the flange surface 36
and the optical fiber filament 46 in layer two 56. By
this geometry each optical fiber layer ends with a half
turn abutting against the flange surface 36, followed by
a half turn, also abutting the flange, which is raised
up to the next layer.
FIG. 5A is a pictorial view showing both plan and
filament end views of a winding made in the manner des-
cribed. For ease of underst~n~;ng, a portion 58 of thebase wire 48 layer is shown with no covering layers, and
similarly several guide wires are left exposed and enu-
merated as 60.
During development of the optical filament winding
64 on the mandrel (FIG. 3), an adhesive binder is applied
to the filament which causes the winding to be maintained
unitary. On completion of the winding, the flanges are
removed and several of the innermost optical filament
layers 66 are pulled out and destroyed which allows the
winding proper to be taken off the mandrel (FIGS. 6A and
6B). The base wire and guide layers can remain on the
mandrel and may be reused. Not only does removing the
sacrificed layers 66 enhance winding removal from the
mandrel, but also reduces filament tensile stresses that
may have been produced during windinq.
1333130
1 The resultant or final winding enumerated as 68
has squared off outer surfaces providing a substantially
rectangular cross-section which is volumetrically effi-
cient (FIG. 2A). Also, since the crossovers are
syLmmetrically arranged filament payout in use can be
made from the inside of the winding without stressing
the filament unduly or producing micro-bending known to
reduce optical signal transmission.
For the following description of a second embodi-
ment of the invention reference should be made to FIG,
SB. The primary difference from the first described
embodiment is the way in which the guide wires are laid
down on the base layer in order to obtain the spaced
apart relation necessary for nesting the larger diameter
filament winding therebetween. The first or base layer
62 may be formed either by winding left to right or
right to left except that the wire ends have to be
secured to the mandrel. The-second or guide layer is
formed by a "bi-filar" technique in which two wires, a
large diameter wire 70 and a smaller diameter wire 72,
are wound side by side to form the entire layer. Then,
the larger diameter wire 70 is removed leaving the
smaller diameter wire 72 nested in the base layer and
spaced apart to receive the optical fiber 46 in the
spaces between the guide wire. The smaller wire then
has its ends secured (not shown) and all else remains
the same.
Although filaments and base wires of other
~;m~n~ions may bé found advantageous, excellent results
were obtained with an optical fiber 46 having a diam.eter
of approximately 0.010 inches, a base wire 48 of 0.005
inches, a large diameter wire 70 of 0.006 inches and a
smaller diameter guide wire 72 of 0.003 inches.
. 133313~
1 Although several somewhat preferred embodiments
have been disclosed and described in detail herein, it
should be understood that this invention is in no
sense limited thereby and its scope is to be determined
by that of the appended claims.
