Note: Descriptions are shown in the official language in which they were submitted.
C~ No. 5~,981
Title: PLASTIC TRANSMISSION E3RAKE BAND
This invention relates generally to transmission
bxake ~ands.
Background and Summary of the Invention
Transmission brake bands now in use are made
substantially entirely of steel components with the usual
friction lining material secured to the inner surface
of the band~ The manufacture of steel brake bands requires
numerous operations, including welding or mechanical
fastening, both in the fabrication of the components
and in the final assembly~
It is a primary object of this invention to
provide a transmissi~n brake band in which the band is
made of a strap of filament-reinforced plastic material.
Such a brake band has many advantages over conventional
steel bands, among which are the following:
1. It can be provided with extra reinforcement
in areas of high loading by adding more layers of filament-
reinforced plastic material. Areas subject to lesser
loading can be provided with a reduced amount of filament-
reinforced plastic material to improve flexibility and
conformability. Also, reinforcing filaments may be so
oriented as to m~X;mi ze strengthJ particularly in high
stress areas.
~ 25 2~ The load-carrying band ends or lugs are
; capable of being molded into the plastic band, so that
the load transfer from the lugs to the strap is evenly
distributed. In conventional designs, the load is
transmitted through welds or rivets which are weak
points.
~lv 2
3. Since the ~ Lament-reinforced material is
only about one quarter ~he weight of steel, brake bands
having straps made with filament-reinforced plastic are
much lighter in weight~
4~ A band having a strap of filament-reinforce~
plas~ic material is capable of being molded in a single
operation. Moreover, the bond between the friction
linin~ and the filament-reinforced plastic strap of
the brake band can be achieved withouk an intermediate
layer of adhesive, since the plastic-saturated filaments
will adhere to the fricti~n lining during polymerization~
An accordance wi-th the invention, there is
provided a friction band comprising an arcuate band
having adjacent end portions adapted to receive the
actuating force. The arcuat~ band between its end
portions comprises an elongated strap of filament-rein
forced plastic material extending from one end portion
of the arcuate band to the other. A strip of friction
material is adhered to the radially inner surface of
the strap of filamen-t-reinforced plastic material. The
strap of plastic material is reinforced by a multiplicity
of continuous, elongated flexible reinforcing filaments
extending lengthwise of the strap and circumferentially
of the arcuate band from one end portion thereof to the
other. The end portions have load transfer lugs and
the strap of filament-reinforced plastic material is
formed in a length which at the ends of the arcuate
band is folcled back circumferentially upon itself and
over the lugs to anchor the lugs in the folds thereof
in a manner such that the loading of the arcuate band,
as transferred by the lugs, is tensiJe and coincident
with the circumferentially extending flexible rein-
forcing elements.
~,
~
2A
Other objects and features of the invention
will become more apparent as ~he following description
proceedst especially when considered with the accompany-
ing drawings.
Brie Description of the Drawings
Fig. 1 is a perspective view showing a portion
of a transmission brake band constructed in accordance
with the ?nvention.
Fis. 2 is a top plan view of the structur~
shown in FigO 1.
Fig. 3 is a fragmenta~y sectional view taken
on the line 3~3 in Fig. ~.
Fig. 4 is a sectional view taken on the line
4-4 in Fig. 2O
Fig. 5 is similar to Fig. 4 but shows a modifi-
cation~~ .
Fig. 6 is a fragmentary ~lan view showing a
portion of a layer of filament-reinforced plastic
material from ~hich the strap of a transmission brake
20 band may be formed~
.
.
3~
Fig. 7 is a sectional view taken on the line
,-7, Fig. 6.
Fig. 8 is a fragmentary side elevational view
showing the end portion of a transmission brake band
of modified construction.
Fig. 9 is a cross-sectional view of the strap
of a transmission brake band of modified construction.
Fig. :L0 is a sectional view of the end portion
of a transmission brake band of modified construction.
Fig. 11 is a cross-sectional view of the strap
of a transmission brake band showing a further modifica-
tio~.
Fig. 12 is a fragmentary top plan view of a
brake band showing still another modificàtion.
Fig. 13 is a sectional view taken on the line
13-13 in Fig. 12.
DETAILED DESCRIPTION
Referring now more particularly to the drawings
and especially to Fig. 1-4, a transmission brake band
is shown composed of an arcuate strap 10 having lugs 11
and 12 of steel ox the like at the adjacent ends of the
strap for receiving the actuating force, and a strip 13
of friction lining material secured to the radially inner
surface of the strap.
The strap 10 is substantially cylindrical
throughout almost a full 360 except for the gap 14
between the ends, The strap 10 is continuous and unin-
terrupted, the portions broken away in Fig. 1 being like
those portions actually shown.
~he strap 10 is ~ade of filament-reinforced
plastic material. A portion of a layer or length 16 of
~ilament-reinforced plastic material from which the
strap is made is shown in Figs. 6 and 7. Such layer 16
consists oE a matrix of plastic material 18 in which are
embedded a multiplicity of filaments 20 arranged parallel
to the length of the layer. Preferably the plastic mate-
ial 18 is thermo~etting epoxy, although other thermo-
setting plastics may be used. There no doubt are sele~tedthermoplastics which may be sui-table,~provided that in
use when the brake band is applied they do not soften from
the heat generated in a particular application.
The reinforcing filaments may be made of many
different materials provided that they meet strength
reguirements. Although glass is the preferred material
of which the filaments are made, examples of other suit-
able materials ar~ boron, graphite, ~evlar (trademark o
DuPont), or a combination of these materials. The fila-
ments are very fine, flexible thread-like strands or ele-
ments (the thickness of the filaments is exaggerated in
the drawings for clarity) and may take many forms such,
for example, as continuous strand rovings, wcven rovings,
woven fabrics, chopped strands and milled fibers.
The strap 10 may consist of one or more layers
16 o the filament-reinforced plastic material~ In the
embodiment shown in Figs. 1-4, there are four such layers,
a~ b, c and d. The inner layers b and c may be parts of
a single continuousor endless member 17 folded upon itself
2S at the adjacent ends of the brake band where indicated at
22 and 24. The outer layers a and d may also be parts
of a single continuous, endless ~embPr 19 likewise folded
back on itself at the adjacent ends of the brake band.
The filaments in the two members 17 and 19 themselves
are,of course, endless.
The lugs 11 and 12 have plate porkions 23 which
are anchored wlthin the folds of the inner layers b and
c at the adjacenk ends of the~brake band. The folded
portions of the filament-reinforced plastic layers forming
the strap 10 may be notched or cut out where indicated at
25 and ~6 to clear the lugs 11 and 12 or the filaments may
be displaced on either side of the load-bearing portion of
the lugs.
The transmission brake band is fvrmed by first
assembling the endless member 17 within the endless member
19 and pressing the members together to form the layers a,
b, c and d, with the plate portions 23 of the lugs 11 and
12 disposed within the folds at the ends of the assembly.
lG The plastic material 18 at this time is in an uncured state
permit-ting -the members 17 and 19 to be pressed and folded
by hand with ease. The assembly is then formed to cylind-
rical shape and placed on a mold or form with a strip 13
of friction material applied to the radially inner surface
of the layer d~ The mold assembly may be placed in an oven
to cure or polymerize the plastic material 18 and set the
transmission brake band in the shape and form shown. When
the plastic material 18 is a thermosetting epoxy, the curing
; temperature of the mold will be approximately 325F. The
curing time may vary from one to several hours, as desired.
A pressure on the order of 100 psi may be applied to the
bra~e band during curing. The filaments 20 are not affect-
ed by the molding operation. The manufacture of the trans-
mission brake band is thus completed.
The strap of the completed brake band is except-
ionally flexible and resilient for compliance with a
braking surface. The curing of the plastic material 18
while in contact with the lugs 11 and 12 and with the
strip 13 of friction material causes the lugs to be
securely and permanently anchored or adhered in the folds
at the ends of the strap and the strip 13 of friction
material to be bonded or adhered permanently to the
radially inner surface of the strap. The bonding of the
luys and the strip 13 of friction material occurs because
the plastic~saturated filaments will adhere to the lugs
and to the strip during the cure or pol~mer:ization of
~3~
the plasti.c in the mold. The plastic-saturated filaments
of the several contacting layers will also adhere to one
another. Whlle not considered necessary, a layer of
adhesive may, if desired, be provided between the friction
strip 13 and the strap 10 to ~enhance the bond.
The filaments 20 extend circumferentially or
lengthwise of the strap 10 continuously from one end of
the brake band to the other, providing sufficient strength
to withstand the normal and even abnormal stresses
1 0
Fig. 5 illustrates a modification which is
like Figs. 1-4 but with an added layer or layers of
filament-reinforced plastic material indicated at 30.
The added layer or layers are wrapped over the layers a,
b, c and d transversely about at least one end portion of
the strap of the brake band so that the filaments thereof
extend at right angles to the direction of l~ngth of the
strap. This transverse wrap 30, of course, is under the
strip 13 of friction material. In Fig~ 5I the added
layers comprise two radially outer layers e and f and two
radially inner layers g and h which may, if desiredt
comprise portions of one continuous length of material
wrapped or wound upon itself. The transverse wrap of
layers are applied to the brake band assembly before it
is put in the mold so that the plastic of the transvere
wrap will cure and set at the same time as layers a, b,
c and d and will adhere to such layers. The transverse
wrap may~ of course, be of the same material as the layers
a, b, c and d.
Fig. 5 is somewhat distorted for purposes of
clari.ty, but it should be understood that during curing
in the mold the transverse wrap will be subjected to
sufficient pressure to flatten its radially inner surface
into substantially the plane o~ the inner layer d of the
strap so that the strip 13 of friction material will be
cylindrical and smooth throughout its full circumferential
extellt. Also it will be understood that the transverse
wrap in Fig. 5 may, for example, extend from the lug at
one end of -the brake band to a point beyond the remote
edge of the lug as seen in Fiy. 1. Naturally, the trans-
verse wrap may be applied to both ends of the brake band.
The transversewrap or wraps provide extra strength to
resist forces that occur at the lugs in a radially outward
direction during lock-up.
Fig. 8 shows a further modification which differs
from Fig. 1 only in tha~ the lug 11 is mechanically fast-
ened to the strap 10 as by rivets 40 or by staking, rather
than by being adhered within a fold of the strap matexial
as in Fig. lo Obviousl~, the other lug may be mechanically
fastened to the strap 10 in a similar manner. The mech-
anical fasteners may be applied after the brake band has
been cured in the mold.
Fig. 9 shows another modification of ~ig. 1 in
which the strap 10 consists of a single layer of filament-
reinforced material and an intermediate layer 50 of flexible,resilient, compressible material is ~onded between the
strap 10 and the strip 13 of friction material. The inter-
mediate layer 50 improves the conformability of the band
strap, allowing the strip 13 to conform to mating surfaces
that do not run true.
Fig. 10 shows a construction like Figs. 1-4
but modified in that one or koth of the band ends are
reinforced by high strength segments 52 of steel or the
like anchored or adhered under the lugs and within the
folds of the filament-reinforced plastic material at
the ends of the strap 10. Note that in Fig. 10 the strap
10 consists of only a single layer of filament-reinforced
plastic material folded over the lug and the steel seg-
ment at one end and terminating at 53~
~53~
Fig 11 shows a further modification of the band
strap 10 which is sh~wnas a single layer of filament-
rein~orced plastic material of full width and having two
narrower, laterally spaced, strips60 of the same
filament-reinforced plastic material extending lengthwise
o~ the strap and bonded in the mold to the radiall~ outer
surface thereof. The narrow strips 60 provide added
strength while retaining exceptionally good transverse
~lexibili-ty for the band~
Figs 12 and 13 show the invention applied to a
so-called double-wrap transmission brake band. This band
has laterally spaced cylindrical strap segments lOa,
lOb and lOc similar to strap 10 previously described,
each having a lug 11 at one end thereof bonded or adhered
15 to end of the filament-reinforced plastic layer 16 of
which the strap segments are made. The layers 16 are
not shown folded over the lugs. Rather the lugs are
bound to the layers 16 by the transverse wraps 30 pre--
viously described, which wrap around the layers 16 and lugs
11~ During curing of the plastic of layers 16 and wraps
30, the plastic-sa-turated filaments 20 become adhered to
each other and to the lugs to form abond. Note the
direction of the filaments 20 of the strap-forming layers
16 and of the transverse wraps 30. The opposite ends of
the segments are integrally joined where indicated at 70
Fig 13 should be understood as showing the band before
curing, when the surface of the friction lining 13 is
irregular where it passes over the transverse wraps.
These irregularities are ~lattened out or disappear in
~0 the finished product because of the pressure employed
during curlng.
