US3160236A - Shoe drum brakes - Google Patents

Description

Deco 8,, 1964 F. T. RIDDY 9 3 SHOE DRUM BRAKES Filed Sept. 24, 1962 5 Sheets-Sheet 1 FREDERICK T R/ooy Dec. 8, 1964 F. T. RIDDY 3,160,236

SHOE DRUM BRAKES Filed Sept. 24, 1952 s Sheets-Sheet 2 FREDERICK T FP/DDY F. T. RIDDY SHOE DRUM BRAKES Dec. 8, 1964 5 Sheets-Sheet 3 Filed Sept. 24, 1962 Dec 8, 1964 F. T. RIDDY 3,160,236

SHOE DRUM BRAKES Filed Sept. 24, 1962 E3 l v FIG 5 5 Sheets-Sheet 4 F. T. RlDDY SHOE DRUM BRAKES Dec. 8, 1964 5 Sheets$heet 5 Filed Sept. 24, 1962 United States Patent 3,169,236 SHUT DRUM BRAKES Frederick Thomas Riddy, Erdington, Birmingham, England, assignor to Sir-ling Limited, Birmingham, England, a British company Filed depto 24, 1962, Ser. No. 225,718 Claims priority, application Great Britain, Sept. 22, 1961, 33,954/ at 6 Claims. (Cl. 188-795) This invention relates to shoe drum brakes and in particular to an automatic adjuster for the shoes of a brake of the kind in which arcuate shoes located within a rotatable drurn are urged apart at one end by an actuator, which may be hydraulic or mechanical or of some other form, and engage at their other ends against a stationary abutment or abutments, the actuator and the abutment or abutments being carried by a stationary backplate.

Various proposals have been made for'automatically adjusting the position of the abutrnents to take up any excessive clearance resulting from wear or" the brake linings, and among these proposals have been arrangements in which movements of the actuator exceeding a predetermined amount cause rotation of a member through a ratchet and pawl mechanism to move the abutments. It is an aim of the invention to provide an improved arrangement of this kind that is economical to manufacture and reliable in operation.

According to the invention there is now proposed a shoe drum brake of the kind set forth in the opening paragraph above in which an automatic adjusting device comprises a lever engaged at one end by a thrust member of the actuator that actuates one of the shoes and connected at its other end to a linkage for adjusting the position of the abutment of at least that shoe, the lever being pivoted directly or indirectly to the backplate at an intermediate point in its length.

When the movement of the moving part of the actuator exceeds a predetermined amount it causes sufficient angular movement of the lever to advance the adjusting linkage for the abutment. Preferably it adjusts the abutments for both shoes simultaneously.

The lever is preferably of arcuate shape, following roughly the web of the associated brake shoe, and is pivoted about an axis perpendicular to the plane of the backplate. Where the actuator has a body that is fixed to the backplate the pivotal axis about which the lever turns can be fixed with respect to the backplate but where the actuator is of the floating type, i.e., its body or in fact all of its parts can move with respect to the backplate, allowing the actuator to centralise itself between the brake shoes even where the linings on'the two shoes wear at different rates, then according to a further feature of the invention the pivotal axis of the lever can be arranged to be linked to movement of the actuator. This can be achieved by mounting that axis on a link which lies close to the lever and is attached at one end to a point near the abutment and at the other end to a part of the actuator itself.

The invention will now be further described by way of example with reference to the accompanying drawings, in in which:

FIGURE 1 is an elevation of a part of a backplate with the actuator and abutment and the adjuster of the invention, one of the brake shoes being indicated in broken line;

FIGURE 2 is a cross-section through the abutment on the line 2-2 in FIGURE 1; 7

FIGURE 3 illustrates a modification of one end of the lever adjuster;

FIGURE 4 is a scrap section on the line 4-4 in FIG- URE 3;

3,l5,235 Fatented Dec. 8, 1964 FIGURE 5 shows a modification in the manner of mounting the lever; and

FIGURE 6 shows a still further modification.

The brake illustrated comprises a backplate 1 carrying two arcuate brake shoes, of which one is shown in broken lines at 2, the other being omitted. The lower ends of both shoes engage abutments in a housing 3 secured to the backplate while, to apply the brake, the upper ends of the shoes are urged apart by an actuator 4. The actuator is not illustrated in detail but it could be mechanical, hydraulic or of any other form, md it will be suflicient for an understanding of the invention to know that it is of the floating type and comprises at least two parts which move apart horizontally (as viewed in FIGURE 1) to act on the shoes. Thebody of the actuator 4 centralises itself between the shoes and a thrust member (not shown) engages the end 5 of the web of the shoe 2. A similar thrust member (not shown) engages the end of the other shoe.

A lug 6 on the body of the actuator 4 carries a pivot pin 7 and a lug 8 on the abutment housing 3 carries a pivot pin 9. Extending between these pivot pins is an arcuate link iii, which lies close to the brake shoe 2 and this link serves as a support for a pin 11 forming the pivotal axis of a lever 12 which is likewise of arcuate shape and lies near the brake shoe 2. It will be seen that the axis of the pin 11 is perpendicular to the plane of the backplate 1 and about one third of the way along the length of the lever 12.. The upper end of the lever 12 forms a thrust pad 13 which is engaged by the same thrustmember of the actuator 4 that engages the end of the shoe 2.

The lower end of the lever 12 has a pin-and-slot connection at 14 with an arm 15 formed on a ring 16 (FIG- URE 2) in the abutment housing 3. The ring 16 forms a one-way clutch or ratchet device embodied in an adjuster for the abutments of the lower ends of both brake shoes. The adjuster works on a known principle and comprises a screw 17 with a coned or pyramidal head 18 between a pair of abutments slidable in the housing 3. One of these abutments is shown at 19 in FIGURE 2 and the other is not shown. A nut 20 in the housing 3 determines the position of the screw 17 and hence the separation of the two abutments, and so rotation of the nut 20 in the appropriate direction will move the abutrnents apart to take up excessive clearance between the brake linings and the drum (not shown). The nut 20 is turned by angular movement of the ring 16 in this direction and is prevented from rotation in the reverse direction by a further one-way clutch device 21 acting between the nut 20 and the housing 3. A screwdriver slot 22 in the screw 17 allows the brake to be adjusted initially or after relining of the shoes.

When the brake is correctly adjusted the thrust member of the actuator 4 and the lever 12 do not move far enough to cause the nut 20 to turn and adjust the brake. But when the lining of the shoe 2 wears the ring 16 is turned far enough to turn the nut 29, and move the abutments 19 apart. On release of the brake the lever 12 is returned to its original position by a spring 23. The movement of the lower end of the lever 12 operates the adjuster screw 17 to take up the clearance that has developed. Preferably the hand of the thread of the screw 17 and the direction of the clutch ring 1 are such that the adjusting operation occurs on the release of the brake rather than on its application as this means that the screw 17 is not working against the brake shoe load at is turns.

In a modification illustrated in FIGURES 3 and 4 of the arrangement shown, the thrust pad 13 is replaced by a tongue or cranked portion 12a of the end of the lever intervening between the thrust member 13a of the actuator and the end of the brake shoe 2. The return movement of the lever on release of the brake is then efiected 3 y the usual retracting springs (not shown) of the brake hoes and the spring 23 can be omitted.

Where the brake is of the kind in which the body 4 f the actuator is fixed on'the backplate" the link 10 can e omitted, and the pivot pin 11 is then mounted directly n the backplate. This is-illustrated in FIGURE 5, which hows an arrangement exactly the same as that of FIG- IRES 1 and 2 and the same reference numerals have een used throughout, the only dilference being that the ivot 11 is mounted directly on the back plate and the ink 16) is omitted together with the lugs 6 and 8 and the ivot pins 7 and 9. The invention is also applicable to rakes of the duo-servo type in which the actuator is lxed to the backplate and the abutment floats. This is tlustrated in FIGURE 6, which shows an actuator 411 nd a. floating abutment 24 in place of the abutment 3. The lower end of the lever 12!) acts on adjusting means 25 n this floating abutment. In this case a link 10a is necssary and as shown this link has a fixed pivot 7a with he actuator 4a and a pivot 9a which is movable with the butment 24. As in the case of lever 12 the lever 12b is ivoted at 11 to the link 10a. The spring 23 serves the ientical function asin FIGS. 1 and which is to act as return spring for the lever 12b. The spring 23 does not erve as a return for the brake shoe inasmuch as these re returned by conventional retracting springs not shown ii any of the drawings.

I claim:

1. A brake comprising a back plate, a drum mounted or rotation about an axis perpendicular to the planetof aid back plate, an arcuate friction-surfaced brake shoe, aid brake shoe being mounted on said back plate within aid drum and and adapted to frictionally engage the nner surface of said drum, an actuator body, shoe- .ctuating means housed within said body and engaging first end of said shoe, abutment means engaging a econd end of said shoe, said actuator body being capable f limited circumferential movement with respect to said ack plate, an adjustable connection between said abutnent means and said second end of the shoe, an arcuate ink extending substantially alongside said shoe, and aivotally connected at its two ends respectively to said ,ctuator body and said abutment means, an arcuate lever xtending substantially alongside said link and shoe, one nd of said lever being engaged by said shoe actuating means and the other end of said lever being operatively pplied to said adjustable connection, and a pivotal con- ;ection between said link and said lever about an axis ntermedi-ate the length of each and perpendicular to he plane of said back plate.

2. A brake comprising a back plate, a drum mounted or rotation about an axis perpendicular to the plane of aid back plate, an \arcuate friction-surfaced brake shoe, aid brake shoe being mounted on said back plate with said drum and adapted to frictionally engage the rmer surface of said drum, an actuator body fixedly counted on said back plate, shoe actuating means housed vithin said body and engaging a first end of said shoe, butment means engaging a second end of said shoe, said butment means being capable of limited circumferential movement with respect to said back plate, an adjustable onnection between said abutment means and said secnd end of the shoe, an arcuate link extending substanially alongside said shoe and pivotally connected at its wo ends respectively to said actuator body and said butment means, an arcuate lever extending substanially alongside said link and shoe, one end of said lever eing engaged by said actuating means and the other rid of said lever being operatively applied to said adlstable connection, and a pivotal connection between aid link and said lever about an axis intermediate the :ngth of each and perpendicular to the plane of said ack plate.

3. A brake comprising a back plate, a drum mounted J1 rotation with respect to said back plate about an axis perpendicular thereto, an arcuate friction-surfaced brake shoe, said brake shoe beingmounted within said drum for limited movement with respect to said back and said brake shoe being adapted to frictionally engage the inner surface of said drum, an actuator body, shoe-actuating means supported on said body, an operative connection between said shoe-actuating means and a first end of said shoe, abutment means, adjustable connecting means between said abutment means and a second end of said shoe, an arcuate lever, said lever extending substantially concurrently with said shoe, one end of said lever lying adjacent said first end of said shoe and being caused to a move therewith, an arcuate link extending substantially concurrently with said shoe and lever, a connection between one end of said link and said actuator body, a connection between the other end of said link and said abutment means, a pivotal connection between said lever and said link at a point intermediate the length of each about an axis perpendicular to said back plate, and an operative connection between said adjustable connecting means and the other end of said lever.

4. A brake comprising a back plate, a drum mounted for rotation about an axis perpendicular to the plane of said back plate, an arcuate friction surfaced brake shoe mounted within said drum and adapted to frictionally engage the inner surface thereof, a shoe actuating member engaging one end of said shoe for applying the brake upon operation of said shoe actuating member, an abutment member engaging the second end of said shoe, one of said members being capable of limited circumferential movement with respect to said back plate, an adjustable connection between said abutment member and the second end of said shoe, an arcuate link extending substantially alongside said shoe and pivotally connected at its two ends respectively to said actuating member and to said abutment member, an arcuate lever extending substantially alongside said link and shoe, one end of said lever being engaged by said actuating member and the other end of said lever being operatively connected to said adjustable connection, and a pivotal connection between said link and said lever about an axis intermediate the length of each and perpendicular to the plane of said back plate.

5'. A brake comprising a back plate, a drum mounted for rotation with respect to said back plate about an axis perpendicular thereto, an arcuate friction-surfaced brake shoe, said brake shoe being mounted within said drum for limited movement with respect to said back plate and said brake shoe being adapted to frictionally engage the inner surface of said drum, an actuator body supporting actuating means, said body being capable of a limited circumferential movement relative to the backplate, an operative connection between said shoe-actuating means and a first end of said shoe, an abutment housing fixedly mounted on the backplate, said housing supporting abutment means, adjustable connecting means between said abutment means and a second end of said shoe, an arcuate lever, said lever extending substantially concurrently with said shoe, one end of said lever lying adjacent said first end of said shoe and being caused to move therewith, an

arcuate link extending substantially concurrently with.

said shoe and lever, a connection between one end of said link and said body, a connection between the other end of said link and said housing, a pivotal connection between said lever and said link at a point intermediate the length of each about an axis perpendicular to said back plate, and an operative connection between said adjustable connecting means and the other end of said lever.

6. The brake of claim 4 wherein said shoe actuating member comprises a body part and an actuator part cooperating with said body part and movable with respect thereto in engagement with one end of said shoe for applying the brake, said abutment member comprising a second body part and an abutment supported by said body part and engaging the second end of said shoe,

5 6 said adjustable connection including adjuster means co- 2,762,463 9/56 Brooks 18879.5 operating with said second body pan: and said abutment 3,034,602 5/62 Bauman 188-79.5 for moving said abutment relative to said second body 3,074,514 1/63 Mossey et a1 188-795 Pan 5 FOREIGN PATENTS References Cited by the Examiner UNITED STATES PATENTS 612,360 11/48 Great Britain. 1,810,628 6/31 Stevens. ARTHUR L. LA POINT, Primary Examiner.

1,824,552 9/31 Khezarjian 188-795 10 2,132,576 10/38 Nachtwey 188-795 GRAHAM cRAVEREmmme

Claims (1)

1. A BRAKE COMPRISING A BACK PLATE, A DRUM MOUNTED FOR ROTATION ABOUT AN AXIS PERPENDICULAR TO THE PLANE OF SAID BACK PLATE, AN ARCUATE FRICTION-SURFACED BRAKE SHOE, SAID BRAKE SHOE BEING MOUNTED ON SAID BACK PLATE WITHIN SAID DRUM AND AND ADAPTED TO FRICTIONALLY ENGAGE THE INNER SURFACE OF SAID DRUM, AND ACTUATOR BODY, SHOEACTUATING MEANS HOUSED WITHIN SAID BODY AND ENGAGING A FIRST END OF SAID SHOE, ABUTMENT MEANS ENGAGING A SECOND END OF SAID SHOE, SAID ACTUATOR BODY BEING CAPABLE OF LIMITED CIRCUMFERENTIAL MOVEMENT WITH RESPECT TO SAID BACK PLATE, AN ADJUSTABLE CONNECTION BETWEEN SAID ABUTMENT MEANS AND SAID SECOND END OF THE SHOE, AN ARCUATE LINK EXTENDING SUBSTANTIALLY ALONGSIDE SAID SHOE, AND PIVOTALLY CONNECTED AT ITS TWO ENDS RESPECTIVELY TO SAID ACTUATOR BODY AND SAID ABUTMENT MEANS, AN ARCUATE LEVER EXTENDING SUBSTANTIALLY ALONGSIDE SAID LINK AND SHOE, ONE END OF SAID LEVER BEING ENGAGED BY SAID SHOE ACTUATING MEANS AND THE OTHER END OF SAID LEVER BEING OPERATIVELY APPLIED TO SAID ADJUSTABLE CONNECTION, AND A PIVOTAL CONNECTION BETWEEN SAID LINK AND SAID LEVER ABOUT AN AXIS INTERMEDIATE THE LENGTH OF EACH AND PERPENDICULAR TO THE PLANE OF SAID BACK PLATE.

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