CA1248885A - Strap configuration for a double wrap band - Google Patents
Strap configuration for a double wrap bandInfo
- Publication number
- CA1248885A CA1248885A CA000489883A CA489883A CA1248885A CA 1248885 A CA1248885 A CA 1248885A CA 000489883 A CA000489883 A CA 000489883A CA 489883 A CA489883 A CA 489883A CA 1248885 A CA1248885 A CA 1248885A
- Authority
- CA
- Canada
- Prior art keywords
- band
- central
- bands
- double wrap
- set forth
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Braking Arrangements (AREA)
Abstract
IMPROVED STRAP CONFIGURATION FOR A DOUBLE WRAP BAND
ABSTRACT
An improved double wrap brake band for the auto-matic transmission of an automotive vehicle wherein the band is lightweight and heat set round at the released position utilizing a thinner stap material at higher hardness ranges. The configuration of the double wrap band has a wider central band segment at the apply end of the central band, with the band width tapering over a substantial fraction of its length so that the re-mainder of its length provides center and outer band widths of substantially equal dimensions; thus providing a double wrap band of increased durability for the friction lining and increased apply and fatigue life.
ABSTRACT
An improved double wrap brake band for the auto-matic transmission of an automotive vehicle wherein the band is lightweight and heat set round at the released position utilizing a thinner stap material at higher hardness ranges. The configuration of the double wrap band has a wider central band segment at the apply end of the central band, with the band width tapering over a substantial fraction of its length so that the re-mainder of its length provides center and outer band widths of substantially equal dimensions; thus providing a double wrap band of increased durability for the friction lining and increased apply and fatigue life.
Description
IMPROVED STRAP CONFIGURATION FOR A DOUBLE WRAP BAND
Description Conventional automatic transmissions transmit torque through what is commonly called a planetary gear system. Planetary gears are in constant mesh and thus cannot clash. They also provide, through arrest of the various gear carrying member, means for drive ratio and direction selection. Brake bands under suitable hy-draulic controls are sometimes used to effect these changes. The bands provide a means of holding gear carriers and usually act as apply force multipliers~ As the governing equation is exponential in nature, a so-called double wrap band may have more than twice the holding power of an otherwise similar single wrap band~
at the expense of increased stroke to full applied position.
Conventionally manufactured double wrap brake bands are formed from a relatively thick metal strap, and a metal forging or casting is secured to the ends of the strap to provide the apply and anchor bracket portions and a transverse tie for the band; the anchor and apply portions or ears being engaged by the struts and a hydraulic piston in the transmission to ~actuate the band. Once the bracket is welded to the strap, the band may be heat treated and the assembly expanded to size, the bracket is transversely broached or milled to form the transverse tie and apply and anchor ears, openings are pierced in the bottom wall of the slots, the inte-rior surface of the band is prepared for bonding and a friction lining applied thereto, openings zre .
, .
:
pierced in the lining, the interior surface is bored and the lining is grooved, and two circumferential slots are sawed through the lining strap and bracket except for the transverse tie portion to result in the three radially expansible bands.
In commonly owned Canadian Patent No. 1,182,379 of February 12, 1985 an improved double wrap band and its method of formation is disclosed which obviates the disadvantages of the internal stresses created in previous bands that lead to distortion of the bands so they are out of round in the released position, thus creating undesirable friction drag between the band and clutch drum and uneven engagement of the band on the drum when actuated. The band of the above application utili~es a stamped slotted thin steel band with transverse tie portions and a stamped bracket with longitudinal tie portions secured thereto. A preslotted friction lining ls applied to the interior of the band and bracket 9 and the tie portions are punched ou~ to form the three parallel band portions having improved roundness in the open position.
The present invention comprehends the provision of an improved double wrap brake band which is formed from a preformed and preslotted stamped strap, a preslotted friction liner and a separate stamped one-piece bracket member; the band and bracket being secured together and the liner applied to the interior surface. The band configuration provides a preslotted stamped strap having equal width bands at one end and a wider central band with narrower outer bands at the opposite end, the wider ;
_.
.. .. .. .
, ~ ' ' ,, '~ ' :, .
385i central band forming with the bracket the apply end which terminates short of the outer bands; the outer bands having widened ends beyond the wide end of the central band. The central band tapers from the wider end to the normal width portion over a substantial fraction of the strap length. The bracket is appro-priately sized for the width of the band ends.
Further objects are to provide a construction of maximum simplicity, efficiency, economy, and ease of assembly, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.
Figure 1 is an eleva~ional view of the preslotted strap utilized in the formation of the improved band.
lS Figure 2 is an elevational view of the band and bracket before removal of the connecting ties.
Figure 3 is an edge elevational view of the band and bracket.
Figure 4 is an enlarged perspective view of the finished double wrap brake band.
Referring more particularly to the disclosure in the drawings wherein is shown an illustrative embodi-ment of the present invention, Figure 1 discloses a preslotted stamped strap 10, utilized in the formation of the aouble wrap brake iard, co-pused of out-r bands . . .
, ~` .
11 and 12 and a central band 13 of substantially equal widths for 50 to 75% of the length of the strap. The strap has parallel longitudinally extending slots 14,14 interrupted by transverse ties 15,15; with the slots diverging at 16,16 for 25 to 50~ of the strap length to provide a tapered central band portion 17 having an end 18 that is of a greater width than the normal band portion 13 and having correspondingly narrower outer band portions 19,19~ The ends 21,21 of the narrow outer band portions extend beyond the center band end 18 and terminate in a width substantially equal to the width of the normal band portions. At the opposite end o~ the strap, the central band end 22 extends beyond the ends 23,23 of the outer bands.
lS A suitable stamped one-piece anchor bracket 24 (Figure 2) is utilized to join the opposite ends of the strap to form a circular brake band 25. The bracket includes a central transverse bar portion 26 of a width equal to the strap width, an anchor portion 27 of the same width as the bar portion, and a centrall~ located apply portion 28; the apply portion and anchor portion being joined to the bar portion by longitudinally extending ties 29. The transverse bar portion 26 is suitably secured, as by spot welding or brazing, to the ends 21,21 of the outer bands 11,12 and the opposite end 22 of the central band 13.
The anchor portion 27 is secured to the ends 23,23 of the outer bands and has a raised bridging portion 31 receiving thereunder the central band 13 adjacent the end 22 secured to the transverse bar portion; the bridging portion allowing for movement of the central , ' ~2~l8~ii band 13 when the double wrap band is applied to the clutch drum or opened. Also, the anchor portion is provided with an upwardly bent or folded transverse ridge 32 extending across the outer bands for app ica-tion by suitable means in the transmission. Also, the apply portion 28 has an upwardly bent or fo~ded ear or lip 33 cooperating with piston means (not shown) in the transmission to tighten the band onto the clutch drum.
The on~-piece anchor bracket member 24 i5 formed into an arcuate member of substantially the same curva-ture as the curved band and secured to the ends thereof as above noted. The assembled unit is heat treated, formed and heat set to the desired diameter over an expanding fixture. ~ preslotted friction lining 34 lS having longitudinally extending slots and transverse ties is bonded to the interior surface of the formed band by a suitable adhesive~ the ties 29 joining the bracket portions are cut out, and then the ties 15 joining the bands of the strap are removed by punching or other suitable operation to form the interconnected three bands 36,37,38 of the final assembly 35 (Figure 4~. As well as having better alignment of the bands and superior roundness for more uniform engagement and lower open running drag, the tapered portion "A"
of the central band provides increased lining durability by allowing a more uniform lining pressure distribution and increased apply end fatigue llfe through reduction of band end flexure. Also, the stamping of the preslot-ted band and the anchor bracket allows use of materials that when suitably processed, result in a higher strength to weight ratio and hence improved ~atigue life over equal weight conventional dbuble wrap bands.
. : ~`, ' . ~, , .
, -` ~' .
8~3~S
The extent of taper of the central band in the preslotted stamped strap is over a substantial fraction of its length and is tailored to the application.
"Substantial fraction", as used herein and in the appended claims, means a range of approximately one-fourth to one-half the length of the central band. In the embodiment shown, which has been successfully built and tested, the fraction is approximately one-third the length of the central band.
Description Conventional automatic transmissions transmit torque through what is commonly called a planetary gear system. Planetary gears are in constant mesh and thus cannot clash. They also provide, through arrest of the various gear carrying member, means for drive ratio and direction selection. Brake bands under suitable hy-draulic controls are sometimes used to effect these changes. The bands provide a means of holding gear carriers and usually act as apply force multipliers~ As the governing equation is exponential in nature, a so-called double wrap band may have more than twice the holding power of an otherwise similar single wrap band~
at the expense of increased stroke to full applied position.
Conventionally manufactured double wrap brake bands are formed from a relatively thick metal strap, and a metal forging or casting is secured to the ends of the strap to provide the apply and anchor bracket portions and a transverse tie for the band; the anchor and apply portions or ears being engaged by the struts and a hydraulic piston in the transmission to ~actuate the band. Once the bracket is welded to the strap, the band may be heat treated and the assembly expanded to size, the bracket is transversely broached or milled to form the transverse tie and apply and anchor ears, openings are pierced in the bottom wall of the slots, the inte-rior surface of the band is prepared for bonding and a friction lining applied thereto, openings zre .
, .
:
pierced in the lining, the interior surface is bored and the lining is grooved, and two circumferential slots are sawed through the lining strap and bracket except for the transverse tie portion to result in the three radially expansible bands.
In commonly owned Canadian Patent No. 1,182,379 of February 12, 1985 an improved double wrap band and its method of formation is disclosed which obviates the disadvantages of the internal stresses created in previous bands that lead to distortion of the bands so they are out of round in the released position, thus creating undesirable friction drag between the band and clutch drum and uneven engagement of the band on the drum when actuated. The band of the above application utili~es a stamped slotted thin steel band with transverse tie portions and a stamped bracket with longitudinal tie portions secured thereto. A preslotted friction lining ls applied to the interior of the band and bracket 9 and the tie portions are punched ou~ to form the three parallel band portions having improved roundness in the open position.
The present invention comprehends the provision of an improved double wrap brake band which is formed from a preformed and preslotted stamped strap, a preslotted friction liner and a separate stamped one-piece bracket member; the band and bracket being secured together and the liner applied to the interior surface. The band configuration provides a preslotted stamped strap having equal width bands at one end and a wider central band with narrower outer bands at the opposite end, the wider ;
_.
.. .. .. .
, ~ ' ' ,, '~ ' :, .
385i central band forming with the bracket the apply end which terminates short of the outer bands; the outer bands having widened ends beyond the wide end of the central band. The central band tapers from the wider end to the normal width portion over a substantial fraction of the strap length. The bracket is appro-priately sized for the width of the band ends.
Further objects are to provide a construction of maximum simplicity, efficiency, economy, and ease of assembly, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.
Figure 1 is an eleva~ional view of the preslotted strap utilized in the formation of the improved band.
lS Figure 2 is an elevational view of the band and bracket before removal of the connecting ties.
Figure 3 is an edge elevational view of the band and bracket.
Figure 4 is an enlarged perspective view of the finished double wrap brake band.
Referring more particularly to the disclosure in the drawings wherein is shown an illustrative embodi-ment of the present invention, Figure 1 discloses a preslotted stamped strap 10, utilized in the formation of the aouble wrap brake iard, co-pused of out-r bands . . .
, ~` .
11 and 12 and a central band 13 of substantially equal widths for 50 to 75% of the length of the strap. The strap has parallel longitudinally extending slots 14,14 interrupted by transverse ties 15,15; with the slots diverging at 16,16 for 25 to 50~ of the strap length to provide a tapered central band portion 17 having an end 18 that is of a greater width than the normal band portion 13 and having correspondingly narrower outer band portions 19,19~ The ends 21,21 of the narrow outer band portions extend beyond the center band end 18 and terminate in a width substantially equal to the width of the normal band portions. At the opposite end o~ the strap, the central band end 22 extends beyond the ends 23,23 of the outer bands.
lS A suitable stamped one-piece anchor bracket 24 (Figure 2) is utilized to join the opposite ends of the strap to form a circular brake band 25. The bracket includes a central transverse bar portion 26 of a width equal to the strap width, an anchor portion 27 of the same width as the bar portion, and a centrall~ located apply portion 28; the apply portion and anchor portion being joined to the bar portion by longitudinally extending ties 29. The transverse bar portion 26 is suitably secured, as by spot welding or brazing, to the ends 21,21 of the outer bands 11,12 and the opposite end 22 of the central band 13.
The anchor portion 27 is secured to the ends 23,23 of the outer bands and has a raised bridging portion 31 receiving thereunder the central band 13 adjacent the end 22 secured to the transverse bar portion; the bridging portion allowing for movement of the central , ' ~2~l8~ii band 13 when the double wrap band is applied to the clutch drum or opened. Also, the anchor portion is provided with an upwardly bent or folded transverse ridge 32 extending across the outer bands for app ica-tion by suitable means in the transmission. Also, the apply portion 28 has an upwardly bent or fo~ded ear or lip 33 cooperating with piston means (not shown) in the transmission to tighten the band onto the clutch drum.
The on~-piece anchor bracket member 24 i5 formed into an arcuate member of substantially the same curva-ture as the curved band and secured to the ends thereof as above noted. The assembled unit is heat treated, formed and heat set to the desired diameter over an expanding fixture. ~ preslotted friction lining 34 lS having longitudinally extending slots and transverse ties is bonded to the interior surface of the formed band by a suitable adhesive~ the ties 29 joining the bracket portions are cut out, and then the ties 15 joining the bands of the strap are removed by punching or other suitable operation to form the interconnected three bands 36,37,38 of the final assembly 35 (Figure 4~. As well as having better alignment of the bands and superior roundness for more uniform engagement and lower open running drag, the tapered portion "A"
of the central band provides increased lining durability by allowing a more uniform lining pressure distribution and increased apply end fatigue llfe through reduction of band end flexure. Also, the stamping of the preslot-ted band and the anchor bracket allows use of materials that when suitably processed, result in a higher strength to weight ratio and hence improved ~atigue life over equal weight conventional dbuble wrap bands.
. : ~`, ' . ~, , .
, -` ~' .
8~3~S
The extent of taper of the central band in the preslotted stamped strap is over a substantial fraction of its length and is tailored to the application.
"Substantial fraction", as used herein and in the appended claims, means a range of approximately one-fourth to one-half the length of the central band. In the embodiment shown, which has been successfully built and tested, the fraction is approximately one-third the length of the central band.
Claims (16)
1. A double wrap brake band including three substantially parallel curved bands joined by a sheet metal bracket member to form a substantially round double wrap band, the bracket member including a trans-verse connecting bar portion joined to one end of each of the three bands, an anchor portion joined to the opposite ends of the outside bands and having a raised central bridging section to allow the central band to pass thereunder, and an apply portion joined to the opposite end of the central band, the outside bands extending from the connecting bar portion in one di-rection and the central band extending from the bar portion in the opposite direction of rotation, said apply portion having an engaging surface receiving the end of an actuating piston and said anchor portion having located surfaces, the improvement comprising the apply end of said central band being tapered over a substantial fraction of its length to provide a widened end for said apply portion of the bracket member.
2. A double wrap brake band as claimed in Claim 1, in which said substantial fraction is in the range from one-fourth to one-half of the central band length.
3. A double wrap brake band as claimed in Claim 1, in which said substantial fraction is approximately one-third the central band length.
4. A double wrap brake band as set forth in Claim 1, wherein said outer bands parallelling said central band have corresponding tapered portions resulting in narrowed band portions adjacent the widened end of said central band.
5. A double wrap brake band as set forth in Claim 4, wherein the narrowed end portions of the outer bands project beyond the widened end of the central band to be secured to said bar portion.
6. A double wrap brake band as set forth in Claim 5, wherein the narrowed end portions of the outer bands terminated in inwardly widened ends beyond the widened end of the central band.
7. A double wrap brake band as set forth in Claim 6, including a friction lining applied to the interior surface of and corresponding in configuration to said outer and central bands.
8. A double wrap brake band as set forth in Claim 6, wherein the widened ends of the outer band have a width substantially eqùal to the width of the opposite ends of the outer bands.
9. A preslotted stamped strap for use in a double wrap brake band, which strap includes three substantial-ly parallel curved bands, the central one of said bands having an apply end and an anchor end, the improvement comprising the apply end of said central band being tapered over a substantial fraction of its length.
10. A preslotted stamped strap as claimed in Claim 9, in which said substantial fraction is in the range from one-fourth to one-half of the central band length.
11. A preslotted stamped strap as claimed in Claim 9, in which said substantial fraction is approximately one-third the central band length.
12. A preslotted stamped strap as set forth in Claim 9, wherein said outer bands parallelling said central band have corresponding tapered portions result-ing in narrowed band portions adjacent the widened end of said central band.
13. A preslotted stamped strap as set forth in Claim 12, wherein the narrowed end portions of the outer bands project beyond the widened end of the central band.
14. A preslotted stamped strap as set forth in Claim 13, wherein the narrowed end portions of the outer bands terminate in inwardly widened ends beyond the widened end of the central band.
15. A preslotted stamped strap as set forth in Claim 14, including a friction lining applied to the interior surface of, and corresponding in configuration to, said outer and central bands.
16. A preslotted stamped strap as set forth in Claim 14, wherein the widened ends of the outer band have a width substantially equal to the width of the opposite ends of the outer bands.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US64760284A | 1984-09-06 | 1984-09-06 | |
| US647,602 | 1984-09-06 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1248885A true CA1248885A (en) | 1989-01-17 |
Family
ID=24597611
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000489883A Expired CA1248885A (en) | 1984-09-06 | 1985-09-03 | Strap configuration for a double wrap band |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1248885A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5476160A (en) * | 1991-10-29 | 1995-12-19 | Borg-Warner Automotive, Inc. | Double-wrap brake band assembly |
| US5499700A (en) * | 1994-12-14 | 1996-03-19 | Borg-Warner Automotive, Inc. | Double wrap brake band with break-away ties |
-
1985
- 1985-09-03 CA CA000489883A patent/CA1248885A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5476160A (en) * | 1991-10-29 | 1995-12-19 | Borg-Warner Automotive, Inc. | Double-wrap brake band assembly |
| US5499700A (en) * | 1994-12-14 | 1996-03-19 | Borg-Warner Automotive, Inc. | Double wrap brake band with break-away ties |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |