Note: Descriptions are shown in the official language in which they were submitted.
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The pxesent in~ention relates to an improvement
in double wrap brake band of the type used in the automa-tic
transmisslon of an automotive vehicle. In a conventional
automatic transmission of the torque converter type, a
driven shaft extends from the torque converter into the
trallsmission to a unit having one or more clutch drums around
which are placed double wrap brake bands; and more specifically J
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 directlon of rotation of the output or drive shaft 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 forgin~
or casting forming ears and a transverse tie for the baIld;
the ear.s 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 o~ the
arcuate strap and the edges of the casting and strap are
butt welded together. As seen in U.S. Patent No. 2,867,898,
once the bracket is welded to the strap, the assembly is
expanded to size and shape, the bracket is transversely broached
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- to form the transverse tie and ears separated by paralLel
slots and to :Eorm "V" slots in the ears to acco~noclate
the struts r openings are piercecl in the bottom wall o:E the
b~oached slots, the interior surface of the assembly is
shot peened and the friction lining is bonded to the surface.
After bonding, openings are pierced in the friction material
the interior surface is bored, the Eriction lining is
circumferen-tially grooved, and two circumferential slots
are formed through the assembly, excep-t the transverse tie,
lQ 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 .n operation. ~ie internal
stresses created in the bands during manufacture will dis~ort
the bands so that they are not round in the released posi~ion.
Thus, when assembled in an automatic transmission, there will
b a certain amount of drag between the bands and its associated
drum~ Also, when -the bands are ac-tuated to engage the drum,
a lack of concentricity o~ the outer and middle bands results
in uneven engagement of the band. The double wrap brake band
of the present invention obviates the disadvantages o~ the
previous~y used bands.
According to the present invention there is provided
a one-piece bracket member adapted for use in the manufacture
of a double wrap brake band, the one-piece bracket member
having transverse connecting bar, anchor and apply portions
connected by longitudinally extending ties. The bracket
member portions are adapted for welding to the opposite ends
of an elongated flat strap with longitudinal parallel slo~s
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and transverse ties interrupting -the slots. After joining
of the brac~et member to the formed strap and cutting ou-t
the ties in the bracket member and the ties in the s-trap,
a double wrap band is completed.
By using the bracket member of this invention an
i.mproved double wrap brake band can be formed from a preEormed
and preslotted stamped strap and the separate stamped one-
piece bracket member. The band and bracket are for~ed ~rom
thinner gauge sheet metal -for improved cost and ligh-ter weight
with the material having a higher hardness range. The bracket
and strap are secured togetherl and the assembly is heat
set round the released positicn to decrease t.he drag of the
band on -the clutch drum ~Jhen the band is released.
More specifically the present invention provides a
unique one-piece bracket member for joining the free ends
of the preslot-ted strap together. The bracket member comprises
an anchor portion having a central bridging section, a
transverse connecting bar and an apply portion; all joined
toge-ther by longitudinally extending generally parallel
ties. The bridging section of the anchor portion connects
the anchor ends of the outer bands together to improve the
ali.gnment of the straps and thereby improves engagement of
the band. Also, the transverse connecting bar is secured to
the static ends of all three bands formed from the strap.
Further objects are to provide a construction oE
maximum simplicity, efficiency, economy and ease of operation,
ancl such further objects, advantages and capabilities as will
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: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 view of the preslotted
strap forming the double wrap band.
Figure 2 is a side elevational view of the st.rap
in a curved condition.
Figure 3 is a top plan view of -the curved strap.
Figure 4 is a side elevational view of the bracket
member of this invention.
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Fi~ure 5 ls a -top plan vie~ o~ t~e hracket
me~er.
~ igure 6 is an enlarsed pexs,pective vie~ of ~he
~racket mem~er.
Fl~ure 7 is a partial slde elevational vle~
of the assem~led strap and b,racket secured toget~er~
Flgure'8 is a top plan vle~ ol ~he assem~ly.
~igure 9 is a top plan'vie~ of the pres~otted
friciion lining lor the ~and.
Fi~ure 10 is a side elevational view o~ the
~and assemhly wit~ the bracket -ties being removed.
E'igure ll is a cross sectional view taken on
the line 11-ll of Figure lO.
Figure 12 is a top plan view of the band
assem~l~ with the bracket tie straps removed.
~ igure 13 is a side elevational view of ~he
baIld assemhly ~ith the strap ties removed.
Figure l~ is a top plan view of a portion of
the ~and shot~in~ the strap tie~ removed.
E'~gure 15 is a top plan vie~ of the f1nal
band assem~
Figure 16 is a cross sectional view ta~en on
t~e line 16-16 of ~igure 15.
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Figure 17, which appears on the same sheet oE
dra~Jings as Figure 6, is a cross sec-tio~al vie~ -taken Otl
the line 17-17 of Figure 15.
Figure 18 is a top plan view of a strap for a
reverse band.
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 assemble~
~racket 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
aligned ties 12 to form parallel outside bands or band
segments 13 and 14 and a middle band or band segment 15.
One end 16 of the middle band extends beyond the ends
1'7,17 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 ~and is ~oxme~
in-to a curved mernber 33 (Fi~ures 2 and 3).
An important aspect of the present inyention
resides in a one-piece anchor bracket member 21 (Figures
4, 5 and 6) formed by stamping the bracket member from
sheet metal to provide a lon~itudinally curved member.
The bracket member 21 includes a
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central transverse connecting ~ar portion 22
having a ~Yidth e~ual to the ~idth o the ~trap l~,
an anc~or portion 23 extend~n~ the wiat~ of the
str~p and havin~ an up~.ardl~ folded or crim~ed
ridge 24 and a raised ce~-tral hridging section or
portl.on 25 on each side of and extending under the
crimped, convex ridge 24; the anchor portion being
int2gral ~it~ t~e transverse connecting bar portion
22 t~rough a pair of parallel ties 26 r 26. T~e
anc~or poxtion 23 of ~racke-t mem~er 21 serves t~e
unique purpose of connecting -t~e anc~or ends 17,17
o~ tho outer bands 13 and 1~ to improve the a igr~erlt
of the ~ands ~3,14 during engagement. A pair o~
upr~ardly bent positioning tahs 27,27 are stamped
out of. the anchor portion adjacent but rear~7ardly
of the ~olded ridge 24; the ta~s or ears 27 functionirlg
as locating mem~ers. Extending from the opposite
side of the transverse connecting bar portion 22 is a
centrally located longitudinally extending apply
portion 28 having an upwardly crimped or folded
lip 29 with an inden-ted central area 31; the apply
portion beina attached to the transverse bar portion
22 by a tie 32.
The anchor bracket memher 21 :is a one-piece
stamping that i~ located on the end~ of the strap
lQ when it is ~ormed or curved into a generally
arcuate member 33 ~ith the central hand 15 extending
under the raised brid~in~ ~ection 25 o~ the hracket
~en~er. The bracket mem~er is spot ~elded as at
3~ to thP ends 16,1~ o:E the middle ~and and t~e
ends 17,17,18,18 of the outer ~ands ~igures 7
and 8i. A~ter spot weIding, the ~racket and
curvea strap may ~e copper ~razed together to
improve the relia~llity over a slrnple welded
assem~ly.
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A~-ter spo-t welding and/or bra~ing at a temperature
in the range of 2030 to 2050 F., the assembly is held for
~ive minutes at t~le elevated tempera-ture and then heat
treated by hea-ting to a temperature in the range of 1550 to
1700 F. and quenched in hot or cold (100 F. - 350 F.) oil
to provide a Rockwell C scale hardness of 54 to 58. Then
the assembly is predrawn at a temperature of approximately
400 F. for about 35 minutes to a Rockwell C scale hardness
of 50 to 54. Finally~ the assembly is heat set to the desix-ed
diameter over an expanding fixture at a temperature in the
range of 700 to 740F. over a time period of 20 to 30
minutes to produce a Rockwell C scale hardness of 40 -to ~5.
The intermediate assembly including the strap wi.th
the anchor bracket member attached thereto is also disclosed
and is claimed in applicant's copending divisional application
serial number , filed September 11, 1984.
A preslotted non-asbestos friction lining 36 (Figure
9) is applied to the interior surface 35 of the band assembly
after the surface is prepared by an acid etch or other suitable
2G surface preparati.on. The lining also is formed with elongated
longitudinal parallel slots 37 separated by transverse ties
38. The ends 39 of the bands formed by the slots are also
joined by ties 41 rather than the open slots of the strap 1~.
The lining .is bonded to the surface 35 by a suitable adhesive
at a temperature in the range of ~00 to 4~0F. at the bond
line for two minutes with the ties 38 aligned with the -ties
12 of the strap 10 and posi-tioning notches 40 aligned with the
ties 26 of the bracket member; the ends of the ].inlng bein~
positioned substantially diametrlcally opposite to the bracket
3G member 21.
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Once the linin~ is bonded to -the band ass~h~
to fonm t~e assemhl~ 42, t~e ti.es 26,26 joinin~
the por-tion 23 to the connecting ~.ar portion 22
and the tie 32 jolning t~e appl~ portion 2~ to ~he
bar portion are cu-t ou-t ~Figures lQ, 11 and 121.
Ther. the ties 12 and 38 in the ~trap and l;ner,
respectively, are removed b~ punc~ing or oth.er
suita~le operati.on CFigures 13 and 14) to form the
interconnecte~ three bands 44,45,46 of ~he final
assem~ 43 (F;gure 151. This assembly ~as a
~etter alignment o~ t~e ~ands due to t~e inter-
~annection of the anchor ends 1.7,17 of the outer
~ands 4~ and 4~ by the ~r dgin~ section 25 in the
~ree or released position -to provide greater
roundness and thus less drag ~etween the bands ana
the clutch. drum. Also, when the band is applied
to the drum, en~agement is more uniform throughout
the three parallel ~ands 44,45,46. Obviously, the
-ties 12 and 38 in the ~and could be initially
removed follo~ed ~y the bracket ties 26 and 32 to
ohtain -the same result.
~ igure 18 discloses an elongated strap 51 to
~orm the reverse douhle wrap band which is generally
similar to the strap 10 in havin~ longitudinally
extending slots. 52 ~ith transverse ties 53; however,
the end 55 of the central ~and 54 extends farther
~eyond the end$ 57 o~ t~e outside ~ands 56 at the
one end and, at the oppo~ite end, the ends 5~ of
the outer ~ands extend ~carther ~eyond the end 58
of the central band. Like~nse -t~e ~racket mem~er 61
(Figures 1~ and 20¦ of t~.e reverse ~ana is more
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elonga-ted with a connecting bar porti.on 62, an anchor
portion 63 connected to -the bar portion by a pair oE elonga-ted
ties 6~, and an apply portion 68 connected to the bar portion
6? by a single elonga-ted tie 69. The anchor portion 63 is
formed wi-th a cen-tral circumferentially extending raised
bridging section 65 having an upwardly bent convex portion
66, and a pair of upwardly bent ears 67,67 punched ou-t of the
member aligned with the ou-ter bands 56 of the elongated strap
51 to receive anchor struts or pins thereagainst.
The apply portion 68 includes a punched out concave
central upwardly extending lip 71 and a p~ir of punched out side
tabs 72,72 slightly rearwardly and laterally of the lip 71
-to positively locate the apply pisLon pin (not chown) against
-the lip 71; the tabs 72,72 preventing lateral misalignment
of the piston. The process of forming -the final double wrap
band assembly for the reverse band is substantially the same
as described and shown in Figures 1 through 17.
The complete double wrap brake band and the method
of forming the same which are also disclosed and claimed in
above identified parent application serial number 396~677O
The double wrap brake band and the method of making
-the same has several technical advantages over presently
manufactured double wrap bands as follows:
1. Less material is utilized for the band
and bracket to provide a lighter wei~ht
unit.
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2~ Lower runnin~ dra~ lo~s on -~he dru~ ~i~h
th~ band in ~he open posi-tion.
3. An improved fatigue li~e for the ~and
resulting rom utiliza-tion o~ a ~i~her
~ardnes~ range.
4. ~here the ~racket and strap are ~raze~
toget~er, there is improved relia~
over.a ~elded only assem~ly.
5. Better alig~meLl~ o~ the ~ands in open
position and better engaged conformity.
. The assem~l~ has a lower unit cost as
stampings are used instead of forgings
and all machining operations are eliminated.
7. There is an improved bonding of the friction
1~ lining to ~he band.
8. A more uniform product is achieved.
9. A non~a5~estos band lining is utili~ed
,
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