CA1195262A - Bracket member for double wrap brake band - Google Patents

Abstract

Abstract:

An improved double wrap brake band (43) for an automatic transmission and the method of making the band wherein the band is lightweight and heat set round at the released open position with the utilization of thinner strap material at higher hardness ranges. The band is formed from a preslotted and preformed strap (10) and a stamped one-piece bracket member (21) secured to the strap (10). The band subassembly is heat treated and heat set, the interior surface is acid etched and a preslotted friction lining (36) applied to the interior treated surface, the subassembly is sized, and the connecting ties for both the strap and bracket member are removed to provide the final band assembly.

Description

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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 -- 1 ~

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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 sb/

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 sb/`r

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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.

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 - rnabillJ

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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.
. - 7 -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.

sb/ :i ~ ~ ~S2~2 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 _ g ~

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 , ~ 11 -. sb/

Claims (17)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A one-piece bracket member adapted for use in the manufacture of a double wrap brake band, said one-piece bracket member having transverse connecting bar, anchor and apply portions connected by longitudinally extending ties, the bracket member portions being adapted for welding to the opposite ends of an elongated flat strap with longitudinal parallel slots and transverse ties interrupting the slots, wherein after joining of the bracket member to the formed strap and cutting out the ties in the bracket member and the ties in the strap, a double wrap band is completed.

2. A bracket member as set forth in claim 1, wherein said bracket member is stamped from sheet metal.

3. A bracket member as set forth in claim 2, wherein said anchor portion has a ridge extending transversely across the bracket member.

4. A bracket member as set forth in claim 2, wherein a lip is formed in the apply portion by folding of the sheet metal of the bracket member.

5. A bracket member as set forth in claim 3, in which said apply lip has a central indentation therein.

6. A bracket member as set forth in claim 2, wherein said apply portion includes an upwardly bent ear stamped out of the member, and a pair of upwardly bent locating tabs positioned laterally and rearwardly of the bent ear.

7. A bracket member as set forth in claim 3, in which said anchor portion ridge comprises an upwardly folded portion extending transversely across said anchor portion.

8. A bracket member as set forth in claim 7, including a pair of upwardly bent tabs stamped out of the anchor portion rearwardly of said ridge.

9. A bracket member as set forth in claim 3, in which said anchor portion ridge comprises a pair of upwardly bent ears stamped out of the anchor portion and aligned with the outside bands of the strap.

10. A bracket member as set forth in claim 9, including an upwardly bent convex transverse portion located rearwardly of said anchor ears and aligned with the central band of the strap.

11. A bracket assembly as set forth in claim 2, wherein said anchor portion has a raised central bridging section joining the outer anchor sections of the anchor portion.

12. A one-piece bracket member adapted for use in the manufacture of a double wrap brake band, said one-piece bracket member having transverse connecting bar, anchor and apply portions connected by longitudinally extending ties, the bracket member portions being adapted for welding to the opposite ends of an elongated flat strap, wherein after joining of the bracket member to the strap and cutting out the ties in the bracket member and separating the strap into multiple parallel band segments, a double wrap band is completed.

13. A bracket member as set forth in claim 12, wherein said bracket member is stamped from sheet metal.

14. A bracket member as set forth in claim 13, wherein said anchor portion has a ridge extending transversely across the bracket member.

15. A bracket member as set forth in claim 13, wherein a lip is formed in the apply portion by folding of the sheet metal of the bracket member.

16. A bracket member as set forth in claim 15, in which said apply lip has an indented central area therein.

17. A bracket member as set forth in claim 14, wherein said apply portion includes an upwardly bent ear stamped out of the member, and a pair of upwardly bent locating tabs positioned laterally and rearwardly of the bent ear.