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WO1988003998A1 - Dispositif de reglage automatique pour frein a tambour - Google Patents

Dispositif de reglage automatique pour frein a tambour Download PDF

Info

Publication number
WO1988003998A1
WO1988003998A1 PCT/GB1987/000803 GB8700803W WO8803998A1 WO 1988003998 A1 WO1988003998 A1 WO 1988003998A1 GB 8700803 W GB8700803 W GB 8700803W WO 8803998 A1 WO8803998 A1 WO 8803998A1
Authority
WO
WIPO (PCT)
Prior art keywords
formation
brake
brake shoe
ratchet wheel
spacer element
Prior art date
Application number
PCT/GB1987/000803
Other languages
English (en)
Inventor
William Ernest Haines
Original Assignee
Automotive Products Plc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Automotive Products Plc filed Critical Automotive Products Plc
Publication of WO1988003998A1 publication Critical patent/WO1988003998A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D65/00—Parts or details
    • F16D65/38—Slack adjusters
    • F16D65/40—Slack adjusters mechanical
    • F16D65/52—Slack adjusters mechanical self-acting in one direction for adjusting excessive play
    • F16D65/56—Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut
    • F16D65/561—Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut for mounting within the confines of a drum brake
    • F16D65/563—Slack adjusters mechanical self-acting in one direction for adjusting excessive play with screw-thread and nut for mounting within the confines of a drum brake arranged adjacent to service brake actuator, e.g. on parking brake lever, and not subjected to service brake force

Definitions

  • the present invention relates to an automatic adjuster for a drum brake, suitable for motor vehicles.
  • a drum brake normally includes a fixed back plate, a pair of arcuate brake shoes mounted on the back plate, expanding means for urging the brake shoes apart generally radially of the back plate and a rotating brake drum, coaxial with the back plate, against which the brake shoes act.
  • Such a brake may have independent service brake and parking brake expanding means.
  • service brake we mean the primary vehicle braking system, usually hydraulically actuable, and by parking brake, the secondary vehicle braking system, usually mechanically actuable.
  • Wear adjusters are normally incorporated in a drum brake to maintain a substantially fixed clearance between the brake shoes and the brake drum, to compensate for wear of the brake shoe linings. Such adjusters are desirable as they maintain the working travel of the expanding means within the range of a vehicle brake actuating system. Automatic operation of wear adjusters, as the brake is actuated, is known. This invention is particularly concerned with wear adjusters for drum brakes having a strut between the hand brake lever pivotted on one shoe, and the other shoe.
  • the pawl and ratchet mechanism is arranged such that upon hydraulic actuation of the brake, relative movement between the brake shoe and strut will cause the pawl to move relative to the ratchet wheel, so that it will engage a tooth of the ratchet wheel and rotate it to effect adjustment of the spacer element.
  • a spring which acts upon the pawl to maintain it in engagement with the spacer element. The spring may also resiliently load the pawl down into engagement with the ratchet wheel.
  • an automatic adjuster for an internal shoe drum brake having a strut extending between a first and second brake shoe is characterised in that the adjuster includes; a spacer element having a wedge portion which acts between the strut and an abutment on said first shoe to vary the effective length of the strut and maintain the appropriate clearance between the brake shoes and brake drum, the spacer element also having a threaded portion which co-operates with a correspondingly threaded ratchet wheel, the ratchet wheel being pivotally mounted with respect to said first brake shoe, so that the spacer element may pivot to remain in engagement with the strut when the first brake shoe moves with respect to the strut; an actuating arm mounted for movement relative to the first brake shoe, said actuating arm having a resilient pawl formation for engagement of the ratchet wheel, a fulcrum formation for engagement with the spacer element and a spring formation arranged to urge the arm towards the spacer element, so as to maintain the fulcrum formation
  • the spring formation will maintain the arm in engagement with the spacer element, so that upon hydraulic actuation of the brake, when said first brake shoe moves relative to the strut, the spacer element will pivot and the arm will follow this movement.
  • This movement of the arm will cause the resilient formation thereon to rotate the ratchet wheel thereby advancing the spacer element and increasing the width of the wedge portion thereof which is interposed between the strut and the abutment on the first brake shoe.
  • the ratchet wheel is mounted between the posts of a trunnion which is pivotally mounted with respect to the first brake shoe.
  • an automatic adjuster for an internal shoe drum brake having a strut extending between a first and second brake shoe is characterised in that the adjuster includes; a spacer element having a wedge portion which acts between the strut and an abutment on said first shoe to vary the effective length of the strut and maintain the appropriate clearance between the brake shoes and brake drum, the spacer element also having a threaded portion which co-operates with a corresponding threaded ratchet wheel, the ratchet wheel being pivotally located with respect to said first brake shoe; an actuating arm with a resilient pawl formation which engages the ratchet wheel; and a chassis plate secured to the first brake shoe, said chassis plate having a formation which overlies the actuating arm and forces the resilient pawl formation down into engagement with the ratchet wheel.
  • Figure 1 is a view of a drum brake assembly to which the invention is applicable;
  • Figure 2 is an exploded view of an automatic adjuster mechanism according to the invention.
  • Figure 3 is an exploded view of an alternative form of automatic adjuster mechanism according to the invention
  • a drum brake assembly having a pair of brake shoes 11 and 12 mounted on a back plate 13.
  • the brake shoes 11 and 12 may be urged apart by a service brake expander in the form of a double acting hydraulic cylinder 14, about a fixed abutment 15.
  • Pull-off springs 16 and 17 are provided to return the brake shoes to their operative positions.
  • a handbrake lever 18 is pivotted to the brake shoe 12 and acts on shoe 11 through a rigid cross strut 19, movement of the lever clockwise (as viewed in Figure 1) about its pivot urging the shoes 11 and 12 apart to apply the handbrake.
  • a rotatable hub 20 carries a brake drum (not shown) which is coaxial with the backing plate 13.
  • the automatic adjuster illustrated in Figure 2 is mounted on the web portion 21 of brake shoe 11.
  • the adjuster comprises a spacer element 22 formed from a flat plate having a wedge portion 23 with divergent edges 24 and 25 and a screw threaded portion 26 which is generally rectangular in cross section with screw threaded formations along its narrower side edges.
  • a trunnion 27 is mounted through an aperture 28 in the web portion 21 so that it is free to rotate relative to the brake shoe 11.
  • a threaded ratchet wheel 29 is located on the trunnion 27 and engages the threaded portion 26 of spacer element 22.
  • the flange portion 34 forms a abutment against which the edge 25 of the wedge portion 23 may bear.
  • An actuating arm 36 made from resilient material, has at one end a pawl formation 38 and at the other end has a flange formation 37. An extention of the flange formation is bent to provide a fulcrum formation 35, a clip formation 33 and a spring formation 39.
  • the actuating arm 36 is located on the rivet 31, between its head and the flange portion 34, by means of the clip formation 33.
  • the spring formation 39 acts against the shoe table 40 to resiliently load the fulcrum formation 35 into engagement with edge 25 of the spacer element 22. in this position the pawl formation 38 will overlie and engage the ratchet wheel 29.
  • a support plate 41 is secured at one end 42 to the web portion 21 of shoe 11 on the opposite side from the spacer element 22, by means of rivet 31.
  • the portion of support plate 41 at end 42 lies against the web portion 21, while at the other end 43, a portion 44 is cranked away from the web portion 21, so that it lies parallel to but is spaced away from web portion 21.
  • the end 43 of support plate 41 is bent perpendicular to the portion 44 so that it abuts the web portion 21.
  • a tab portion 45 is provided at the end 43 and locates in a hole 46 in the web portion 21, to position the support plate so that portion 44 underlies the aperture 28 in the web portion 21.
  • a corresponding aperture 47 is provided in portion 44 of the support plate 41 through which the trunnion 27 extends, so that a shoulder 48 on the trunnion 27 abuts the upper edge of the web portion 21.
  • a retaining clip 52 has a circlip portion 53 which engages in a circumferential groove 50 in the trunnion 27 and abuts the under side of portion 44 of support plate 41, to retain the trunnion 27 in position.
  • the retaining clip 52 has a tab formation 54 which is bent around the edge of plate 41 and between the posts of trunnion 27.
  • the tab formation 54 is divided into two resilient fingers 55 and 56, which extend into engagement with ratchet wheel 29.
  • Finger 55 is longer than finger 56 by half the pitch of the teeth 57 of the ratchet wheel 29, so that at one position of the ratchet wheel 29, finger 56 will engage the radial face 58 of one tooth 57 and upon rotation of the ratchet wheel 29 by half a tooth pitch, finger 55 will engage the radial face 58 of the same tooth 57. A further turn of half a tooth pitch will then bring finger 56 into abutment with the radial face 58 of the next tooth 57, and so on.
  • Pivotting of the spacer element 22 will also allow the actuating arm 36 to pivot and pawl formation 38 will move relative to ratchet wheel 29. If movement of the pawl formation 38 is sufficient to bring it into engagement with a radial face 58 of one of the teeth 57 of the ratchet wheel 29, it will rotate ratchet wheel 29 and interaction of the screw thread thereof with the screw threaded portion
  • spacer element 22 will cause the spacer element 22 to advance between the end of strut 19 and flange portion 34, so that the effective width of the wedge portion 23 positioned therebetween will be increased.
  • Rotation of the ratchet wheel 29 in the direction to effect adjustment of the spacer element 22, is permitted by the resilient fingers 55 and 56, which ride up the inclined faces of the ratchet teeth 57.
  • the spacer element 22 Upon release of the service brake, the spacer element 22 will pivot back against the action of spring formation 39 until edge 25 again engages flange portion 34.
  • the effective length of the rigid strut 19 between the brake shoe 11 and the handbrake lever 20 is thereby effectively increased, thus increasing the distance between the brake shoes 11 and 12 and compensating for any increase in the gap between the friction linings of the brake shoes 11 and 12 and the brake drum, due to wear of the friction linings.
  • the length of the actuating arm 36, pitch of the teeth of the ratchet wheel 29, pitch of the threads of the ratchet wheel 29 and portion 26 of spacer element 22 and the divergence of edges 24 and 25 of spacer element 22 are selected, such that the incremental adjustment produced by movement of the ratchet wheel 29 by one tooth, will maintain " the gap between the friction linings and the brake drum within desired tolerances, which lie between the minimum running clearance required and the maximum travel permitted by a handbrake mechanism.
  • the actuating arm 36 is located on a shouldered rivet 61 by means of an aperture 62.
  • a chassis plate 63 is secured on the same side of the web portion 21 as the spacer element 22, at one end to the upper end of rivet 61.
  • the other end of the chassis plate 63 is provided with an aperture 64 through which an extention of the trunnion 27 extends.
  • a retaining clip 69 is used to locate the trunnion 27. This clip 69 is similar to clip 52 used in the embodiment illustrated in Figure 2, but the resilient fingers 55 and 56 extend in the same plane as the clip portion 53.
  • the end 66 of the chassis plate 63 is bent at right angles towards the web portion 21 and a tab portion 65 locates in a hole 46 in the web portion 21, to position the chassis plate 63.
  • the chassis plate 63 is cranked between the rivet 61 and the trunnion 27, so that the portion adjacent rivet 61 overlies the actuating arm 36 while the portion adjacent the trunnion 27 underlies the actuating arm 36, the pawl formation 38 extending around the cranked portion to engage the ratchet wheel 29.
  • a guide formation 67 on the portion of the chassis plate 63 adjacent rivet 61 engages actuating arm 36 and loads it into engagement with the ratchet wheel 29.
  • a further formation 68 on the portion of the chassis plate 63 adjacent the trunnion 27 provides a guard for the threaded portion 26 of the spacer element 22.
  • the adjuster mechanism may be preassembled on the chassis plate 63 and subsequently assembled on the web portion 21 of brake shoe 11, by inserting the trunnion 27 through aperture 28, locating tab portion 65 in hole 46 and securing the rivet through hole 32.
  • a pivot post may be secured to the web portion 21, support plate 41 and/or chassis plate 63 by a releasable fastening, for example a circlip.
  • a releasable fastening for example a circlip.
  • the screw threaded portion 26 may be offset from the wedge portion 23.
  • the trunnion 27 is supported by the web portion 21 and support plate 41, the trunnion 27 may however be supported by the web portion 21 only, in which case the retainer clip 52 will abut against the under side of the web portion 21 and the tab portion 54 will extend around the edge thereof and between the posts of the trunnion 27. Also while it is advantageous to divide the tab portion 54 into two resilient fingers of differing length, it may define a single resilient finger.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Braking Arrangements (AREA)

Abstract

Un dispositif de réglage automatique, pour un frein à tambour à sabots internes pourvu d'une barre comprimée (19) s'étendant entre un premier et un second sabot de frein (11 et 12), comprend un élément d'espacement (22) servant à régler la longueur effective de la barre comprimée (19), de façon à maintenir l'espacement approprié entre les sabots de frein (11 et 12) et le tambour de frein. L'élément d'espacement (22) comprend une partie à filet de vis (26) qui coopère avec une roue à rochet à filet correspondant (29), laquelle est montée de façon pivotante par rapport au premier sabot de frein (11) de sorte que l'élément d'espacement (22) puisse pivoter pour rester en prise avec la barre comprimée (19) lorsque le premier sabot de frein (11) se déplace par rapport à la barre comprimée (19). Un bras d'actionnement (36) est monté de façon à se déplacer par rapport au premier sabot de frein (11) et comporte une pièce profilée à cliquet résilient (38) destinée à permettre l'engrènement de la roue à rochet, une pièce profilée à palier (37) destinée à permettre l'engagement de l'élément d'espacement (22) et une pièce profilée à ressort (39) destinée à plaquer le bras d'actionnement (36) contre l'élément d'espacement (22), de façon à maintenir la pièce profilée à palier (37) en prise avec lui. Une plaque de châssis (63) peut recouvrir le bras d'actionnement (36), une pièce profilée (68) qui est disposée sur la plaque de châssis (63) agissant conjointement avec la pièce profilée à cliquet (38) afin de la forcer à s'engrener avec la roue à rochet (29).
PCT/GB1987/000803 1986-11-21 1987-11-11 Dispositif de reglage automatique pour frein a tambour WO1988003998A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB868627907A GB8627907D0 (en) 1986-11-21 1986-11-21 Automatic adjuster for drum brake
GB8627907 1986-11-21

Publications (1)

Publication Number Publication Date
WO1988003998A1 true WO1988003998A1 (fr) 1988-06-02

Family

ID=10607733

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1987/000803 WO1988003998A1 (fr) 1986-11-21 1987-11-11 Dispositif de reglage automatique pour frein a tambour

Country Status (2)

Country Link
GB (1) GB8627907D0 (fr)
WO (1) WO1988003998A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2058970A (en) * 1979-08-31 1981-04-15 Automotive Prod Co Ltd Automatic wear adjuster for drum brakes
EP0049583A1 (fr) * 1980-10-02 1982-04-14 Automotive Products Public Limited Company Dispositif automatique de rattrapage d'usure pour freins à tambour
EP0225749A1 (fr) * 1985-12-13 1987-06-16 Automotive Products Public Limited Company Dispositif automatique de rattrapage du jeu pour frein à tambour

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2058970A (en) * 1979-08-31 1981-04-15 Automotive Prod Co Ltd Automatic wear adjuster for drum brakes
EP0049583A1 (fr) * 1980-10-02 1982-04-14 Automotive Products Public Limited Company Dispositif automatique de rattrapage d'usure pour freins à tambour
EP0225749A1 (fr) * 1985-12-13 1987-06-16 Automotive Products Public Limited Company Dispositif automatique de rattrapage du jeu pour frein à tambour

Also Published As

Publication number Publication date
GB8627907D0 (en) 1986-12-31

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