Note: Descriptions are shown in the official language in which they were submitted.
63
The p-esent inventlon relates to an improvement
in double wrap brake band of the type used in the automatic
transmission OL an automotive vehicle. In a conven-~ion~L
automatic transmission ol the torque converter type, a
driven shaft extends from the torque conver-ter into the
transmission to a unit having one or more clutch drums around
which are placed double wrap brake bands; and more specifically,
the double wrap bands are used for the 1-2 unit and for the
reverse unit. It is the function of the brake bands under
suitable hydraulic controls to effect gear change and control
of the direction of rotation o~ the output or drive shaEt from
-the transmission.
This is a division of copending Canadian Patent
Application serial number 396,677, filed February 19, 1982.
Presently manufactured double wrap brake bands are
formed from a relatively thick metal strap and a forging
or casting forming ears and a transverse tie for the band;
the ears being engaged by the struts and a hydraulic piston
in the transmission to actuate the band. The forging or
casting is located in the space between the ends of the
arcuate strap and the edcJes of the casting and strap are
butt welded together. As seen in U.S. Patent No. 2,867,89~,
once the bracket is welded to the strap, khe assembly is
expanded to size and shape, the bracket is transversely broachecl
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to Eorm the transverse tie and ears separa-ted by par~llel
slcts and to form "V" slots in the ears to ~ccommodate the
struts, openings are pierced in the bottom wall of the broached
slots, the interior surface of the assembly is shot peened
and the friction lining is bonded to the surEace. AE-ter
bonding, openings are pierced in the friction material, -the
interior surface is bored, the friction lining is
circ~nferentially grooved, and two circumferential slots are
formed through the assembly, except the transverse tie, by
sawing through the strap and lining to produce the three
radially expansible bands.
The double wrap bands made by the above enumerated
method have certain disadvantages in operation. The internal
stresses created in the bands during manufacture will distort
the bands so that they are not round in the released position.
Thus, when assembled in an automatic transmission, there will
be a certain amount of drag between the bands and its associated
drum. Also, when the bands are actuated to engage the drum,
a lack of concentricity of the outer and middle bands results
in uneven engagement of the band. The double wrap brake band
of the present invention obviates the disadvan-tages of the
previously used bands.
The present invention relates to an intermediate
assembly in the process of forming a double wrap b~ake band
including an elongated curved sheet metal strap having
longitudinally extending elongated parallel slots separated
ky transverse ties and generally defining three parallel bands.
The slots open into both ends of the strap, and an anchor
bracket member is secured to the opposite ends o~ the strap.
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rrhe bracket member includes a transverse connectin~ bar
portion, a transverse anchor portion joined -to the connec~in~
bar portion by parallel ties, and a central apply portion
on the opposite side of the connec-ting bar portion and
attached thereto by a longitudinally extending tie.
More specifically, the present invention comprehends,
therefore, the provision of an improved double wrap brake band
which is formed from a preformed and preslotted stamped s-trap
and a separate stamped one-piece bracket member. The band and
bracket may be formed from thinner gauge sheet metal for
improved cost and lighter weight with the material having a
higher hardness range. The bracket and strap are secured
toyether, and the assembly may then be heat set round in the
released position to decrease the drag of the band on the
clutch drum when the band is released.
Anillustrated embodiment o-f the present invention
also comprehends the provision of an improved double wrap
brake band utilizing a preslot-ted non-asbestos friction lining.
Less material is required for the band, and there is better
axial alignment of the outside and middle bands in the free
position. ~lso, there is a better engaged conformity of the
double wrap ban~ with all three bands in substantially uniform
engagement with the clutch drum.
In a specific embodiment of the present invention,
the preslotted strap is formed into a curved confi~uration
and a preslotted metal bracket member is spot wel~ed to the
strap; both the strap and bracket having tie portions
retaining a unitary assembly. The assembly is heat treated,
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hea-t set and the interior surface prepared for bonding. A
preslot-ted friction lining is bonded to the interior surface
of the band, and the ties in the strap and bracket are
removed to provide the final double wrap band.
Further objects are ~o provide a construction
of maximum simplicity, efficiency, economy and ease of
operation, and such further objects, advantages and
capabilities as will later more fully appear and are
inherently possessed thereby.
One way of carrying out the invention is described
in detail below with reference to drawings which illustrate
only one specific embodiment, in which:
Figure 1 is a top plan vlew of the preslo-tted
strap forming the double wrap band.
Figure 2 is a side elevational view of the
strap in a curved condition.
Figure 3 is a top plan view of the curved strap.
Figure ~ is a side elevational view of the bracke-t
member for the band.
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Figure 5 is a top plan vle~ o~ t~e hracket
mem~er.
~ igure 6 is an enlar~d perspective vi.e~ o~ ~he
~racket me~er.
Figure 7 is a partlal slde elevati.onal view
o~ the assem~led strap and ~racket secured toge~her in
accordance with this invention.
Figure 8 i5 a top plan vîe~ of the assem~
Fiyure 9 is a top plan vie~ o~ the preslottea
friction lining ~or the ~and.
Flgure 1~ is a side elevational v.iew o~ the
~and assemhly with the ~racket ties ~eing removed~
Figure 11 is a cross sectional view taken on
the line 11-11 of Figure 10.
Fl~ure 12 is a top plan view of ~he ~and
assemfil~ with the bracket tie straps removed.
Figure 13 is a s.ide elevational view of the
~and a5sem~1~ ~ith the strap ties removed.
Fi.~ure 14 i5 a top plan vie~ o~ a portion of
the ~and sho~i.n~ the stra~ tie~ removed.
F~gure 15 is a top plan vi.e~ o~ the f.inal
- ~md assem~
Figure 16 is a cross sectional view taken on
t~e line 16-16 o~ Figure 15~
~ ;gure 17, ~ihich appears on the same sheet oE
dra~ings as Figure 6, is a cross sectional view -taken on
-the line 17-17 oE ~igure 15.
Figure 18 is a top plan view or a strap for a
reverse ~and.
Figure 19 is a side elevational view of the
bracket and strap with the bracket ties removed.
Figure 20 is a top plan view of the assembled
bracket and strap.
Referring more particularly to the disclosure in
the drawings wherein are shown illustrative embodiments
of the present invention, Figure 1 discloses the pre-
slotted flat strap 10 which forms the basis for the final
double wrap brake band. The strap includes two parallel
lines of elongated slots 11 separated by transversely
ali~ned ties 12 to form parallel outside bands or band
2~ seyments 13 and 14 and a middle band or band segment 15
One end 16 of the middle band extends beyond the ends
. 17,17 of the outside band, while at the opposite end,
the ends 18,18 of the outside bands project beyond the
end 19 of the middle band. The slotted band is formed
, into a cwrved member 33 (Fi~ures 2 and 3).
~ An important aspect of the preSQnt in~ention
resides in a one-piece anchor bracket- member 21 (Figures
~, 5 and 6) formed by stamping the bracket member from
30 sheet metal to provide a longitudinally curved member.
The bracket member 21 includes a
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central ~ransverse connecting har portion 22 haviIlg a wid-th
e~ual to -the width o~ -the stxap 10, an anchor portion 23
extending the ~idth oE the strap and having an upwardly foldecl
or crimped rldge 2~ and a raised central ~ridging section or
portion 2~ on each side of an extending under the crimp~d,
convex ridge 2~; the anchor por-tion being integral with the
transverse connecting bar portion 22 throuyh a pair o~ parallel
ties 26,26. The anchor portion 23 of bracket member 21 serves
the unique purpose of connecting the anchor ends 17,17 of the
outer bands 13 and 14 to improve the alignment of the bands
13,14 during engagement. A pair of upwardly bent positioning
tabs 27,27 are stamped out of the anchor portion adjacent but
rea-wal^dly of the folded ridge 24; the tabs or earC, 27
functioning as locating members. ~xtending from the opposite
side of the transverse connecting bar portion 22 is a
cen-trally located longitudinally extending apply portion 28
havirlg an upwardly crimped or folded lip 29 with an indented
central area 31; the apply portion being attached to the
transverse bar portion 22 by a tie 32.
The above described bracket member is also disclosed
and is claimed in applicant's copending divisional application
serial number , filed Sep-tember 11, 1984.
The anchor bracket member 2:L i9 a one-piece stamping
that is located on the ends of the strap 10 when it is Eormed
or curved into a generally arcuate member 33 with the central
band 15 extending under the raised bridying section 25 of the
bracket member. The bracket member is spot welded as at 34 to
the ends 16,19 of the middle band and the ends 17,17,18,18 of
the outer bands (Figures 7 and 8). After s~ot welding, the bracket and curved
strap may be copper brazed to~ether to impxove the reliability over a simple
we.~led assembly.
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After spot ~elding and~or brazing at a
-temperature in the range OL 2Q30 to 2Q50~., the
- asse~bly is held for five minutes at the elevated
iemperature and then heat treated ~y neating t~ a
~emperature in t~e range o~ 155Q to 17Q0.F~ and
quenched in hot or cold ClQQF. - 35~~.1 oil
to provide a Rock~ell C scale ~ardness of 54 to 58.
Then the asse~l~ is predrawn at a ternperature of
approximately 40Q~ for about 35 minutes to a
1~ Roc~w~ll C scale hardness of 50 to S4. Finally,
. t~e assernhly i5 ~eat set to the desired diarneter
over an expanding fi~ture at a temperature i.n t~e
range of 700 to 740 F. over a time period of 20
to 30 minutes to produce a Rockwell C scale hardness
~5 of 40 -to ~5.
A preslotted non-asbestos friction lining 36
(Figure 9~ is applied to the interior surface 35
of the band assem~ly after the surface is prepared
by an acid etch or other suitable surface preparation~
2a The linin~ also is forrned with elongated longituctinal
parallel slots 37 separated ~y trans~erse ties 38.
The ends 39 of the bands ~ormed by the slots are
also joined by ties ~1 rather than the open slots
of the strap 10. The lining is bonded to the
sur~ace 35 by a 5ui.table adhesi~e at a temperature
in -the range of 400 to 44Q F. at th.e ~ond line for
two minutes ~ith ~he tie~ 38 aligned with the ties
12 o the strap ln and po~itioning notches 40 aligned
~ri-th the ties 26 of the bracket rnernberi t~e ends of the
lin~ng ~eing positioned su~stantially diame-trically
opposite to -the ~racke-t mem~.er 21.
Once the lining is bonded to the hand assemhl~
to form the assembly 42~ the ties 26,26 joini.n~
the portion 23 to t~e connecting ~.ar portion 22
and the tie 32 joining the apply portion 2~ to the
~ar portion are cut out ~igures lQ, 11 and 121-
Then tne ties 12 and 38 in t~e trap and liner;
respectivel~, are removed ~ punc~ng or other
suita~le operati.on CFigures 13 and 14l to form the
interconnected three ~ands 44,45,46 of the final
asser~ 43 tFigure 15~.. This a~sembly has a
~etter alignment of the ~ands due to the inter-
connection of the anchor ends 17,17 of the outer
bands 44 and 46 ~y t~e ~ridging sectlon 25 in the
..ree or released position to provide greater
roundness and t~us less drag between -the ~ands and
the clutch drum. Also, when the band is applied
to the drum~ engagemenk i5 more uniform throughou~
-the three parallel bands 44,45,46. Obviously, ~he
-ties 12 and 38 in the band could be initially
. 20 removed follo~ed by the bracket ties 26 and 32 -to
obtain the same result.
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Flgure 18 discloses an elongated strap 51 to
form t~e reverse double wrap band which is generally
similar ta the strap 10 in having longitudinall~
e~tending slot~ 52 w.~th transverse ties 53; however,
the end 55 of the central ~and 54 ex-tends farther
~e~ond the end~ 57 o~ the outside hands 56 ~t the
one end and, a-t the opposite end, the ends 5~ of
th.e outer hands extend ~arther be~ond the end 58
- of the central band. Like~ise the ~racket member 61
(Figures 19 and 201 of the reverse bznd îs more
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elon~atecl with a con~e~ a~ 3 ort~on 62, an anchor
portion 63 connected to the har portion by a pair o.E eloncJa-ted
ties 6~, and an apply poxtion 68 connecLed -to the bar portion
6~ by a sin~le elon-~a-ted tie 69. Tne anchor portion 63 i~
formed with a central circumferentially e~tending raised
bridging section 65 having an upwardly bent convex portion
66, and a pair o~ up;~lardly bent ears 67,67 punched out of the
mernber aligned with the ou-ter bands 56 of the elongated s~rap
51 to receive anchor struts or pins thereagains-t.
lC) The apply por-tion 68 includes a punched out concave
cen-tral upwardly extending lip 71 and a pair of punched out side
tabs 72,72 sliyhtly rearwardly and laterally o-f the lip 71
to positively locate the apply piston pin (not sho~n) against
the lip 71; the tabs 72,7~ preventing laieral misalignment
of the piston. The process of forming he final double wrap
band assembly for the reverse band is substan-tially -the same
as described and shown in Figures 1 through 17.
The complete double wrap brake band and the method
or Eorming the same which are also disclosed and claimed in
above-identified paren-t application serial number 396,677.
The double wrap brake band and the method of making
the same has sevexal technical advantayes over presently
manufactured double wrap bands as follo~.is:
1. Less material is utilized -for the band
and bracket to provide a lighter weight
unit.
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2. Lower running dra~ loss on -the drum ~it~
the ~and in ~he open position.
3. An improved facigue life for -the ~and
resulting from u-tilization of a hîg~er
hardness range.
4. W~ere the ~racket and strap are brazed
together, t~ere is improved relia~ilit~
over a welded only assem~ly.
5~ Better alig~nent of t~e ~ands in open
position and better engaged conformity.
5. The assem~ly has a lower unit cost as
stampings are used instead of forgings
and all machining operations are eliminatea.
7. There is an improved bonding of the friction
lining to the band.
8. A more uni~orrn product is achieved.
9. A non-as~e~tos band lining is utilized.
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